Oh OP.... I don't even know where to start. It took me so long to answer because I would've been so incohesive spamming my MANY thoughts about his dancing without order, and tbh Im still winging it as i respond rn! 😭 (Update upon finishing: Please expect a chronological observation of his dancing across eras, and then my personal viewpoints of his dancing in a still-objective ish lens right after. omg isaid so much)

Before I can talk about my Own take, I want to share where I'm coming from by describing his milestones in dancing.

Back in pre-debut, his dance style was all about force and moving explosively, widely, energetic to maximize the movement like any hobbyist dancer. He already has a good sense of rhythm back then, and only lacked personal texture. It's like his arm juts out as you would a punch on your first day of boxing, fast and straightforward.
He started forming it especially during debut, under both professional mentorship and guidance by his own dance hyungs, especially lee know and hyunjin.
In their earliest days, he still retained some of that force-first dancing that tries very hard to announce his stage presence, and has also developed the flavor of sentiment especially during I Am series' more emotional songs and choreo (Mirror, I am You).
By 2019 and the cle series, it's when I saw him start utilizing more control and precision in his body angles, taking up space onstage, and experimenting with texture, the speed with which he carries out the smaller details of their dancing, waves and arm motions and how he glides across the stage. I feel like this was especially expedited by him having such a central role in Levanter's title track choreo, where he had to express so much emotion and still maintain that control. He hit a ceiling and he's clambering out of it!

Come GoLive and InLife, we see him start to explode with improvement as a whole. Seungmin took the skills he was most comfortable in and used them to scaffold where he lacked. Gods Menu forced him to learn how to burst with energy right from the get go and still have enough breath for his own parts repeatedly in phases, while Back Door pushed him to be stable during heavy movement. These are 2 foundational skills he continued working on to the point that they are his greatest assets today.

For the past title tracks, he grasped these expressions at a general level, similar to the furrowed brows and slight for when you ask someone to give an angry expression out of the blue. After developing foundations of stability and conservation, Kingdom is when he has moved on to forming the type of suave, smug, looming, vaguely threatening aura or stage presence he naturally slips into at present. Seungmin started Really using his eyes, swagger, and angling shoulders to impose a sense or presence upon the audience at a time when there was global and professional scrutiny rather than a live audience seated far from the stage who probably can't really See facial details that well. He really worked to cement himself in Thunderous itself, putting into practice everything he's developed thus far.

I believe one of the "loudest" developments started during Oddinary. It's like he's pursuing a post doc on his brand of dancing: Mastery of basics (undergrad and masters) and the beginning of specialization(post-doc).

Things got increasingly harder for him as a dancer since Oddinary, I believe, He mentioned before that MANIAC was very challenging compared to past choreo because there was really no time given for him to breathe, even if it was overall less intense. I have always seen him positioned in the back or given rest time at the side before or after his parts so he could rest, but MANIAC was the start of him racking up his stamina out of need for longer than he's used to. And then the world tour happened, and this stamina increased exponentially with up to 3 INTENSE performances up to 12 minutes each followed and lead by a few more. The boundaries of his energy was challenged and pushed outwards.
We see this newfound tank of energy with 5-STAR with its consistently grueling choreo ALL throughout their songs that now involve full-body intensity and non-stop and very-large movements, mostly for the arms too (see s-class, item, hall of fame, and superbowl...thats practically everything they performed lmao). This was when everything he has developed so far has been put to the test. The impact of his dance style became more than the sum of all its parts, and I believe that this is a large part of why he shines so much right now, as all the pieces have finally clicked into place and he's rolling with it HARD.

The thing with any skill is that the more you master processes and details, the less you have to think about them or be conscious of them, and the more space you have to think about ways to make it better. Because he has reached mastery over a large aspect of the mechanics or movements of dancing, he now has enough mental space to explore style, swagger, injecting his sly doberman persona in the performance. He has expanded his expressions and made natural the most Seungmin brand of piercing gaze, cocky and an untouchably threatening flair.

With that said, ROCK star is when he started experimenting with how expressive he could be with his body. A little less shy now, a little less conservative. Stamina was his biggest hurdle his biggest limiter, and now its not even something he worries about as he explores energy and expressiveness in every stage. A year of touring with POPPIN, and a few months worth of body rolls in Hall of Fame opened him to the idea of maybe bringing the lower wave upwards to his torso, and now he body rolls with more ease for LALALALA's own rolls, a little less conservative and shy with how he can utilize his body.

How would I describe his style now?

Clean
I believe he's one of the cleanest dancers in SKZ, and by clean I mean precise and clear where you can see the intention of the choreo. Seungmin knows his body very well now, that the balance of his postures and the weight distribution when he dances is the best it has ever looked. He developed a strong intuition for texture; there is grace where there is no force, and a punch where there is no sway. He stays within the range of a stable center of gravity. With these, Seungmin is one of those that hold visual coherence within the group choreo, right beside Chan, Changbin, Felix, while Han, Hyunjin, Lee Know, and I.N are in charge of the in-your-face factor of ballistic explosiveness. (God I'm so proud of all of them). If you have a whole group full of furious stylized flair like HyunMinJeongSung, it could look uncoordinated from the sheer range of what everyone can do.

Stable
Changbin once said around ODDINARY era during a magazine interview somewhere that he really appreciated the vocalists because it takes a different kind of endurance to be so stable throughout the nonstop dancing for MANIAC. Stability defined as the ability to fulfill the basic skills without flustering or staggering seems basic, but it's the foundation where everything else you can do will be built upon: You can't think of expressions to woo the crowd when you're a second past passing out. He is completely in tune with what he can and can't do, and you can see throughout all his fancams how consistent his energy is in each performance no matter the conditions of the day as product of his efficiency.

Compelling
I recall one of JYP's rare critiques on him during the survival show: Seungmin was good at what he did, but he did nothing that stood out. There was a period of time you had to look for who was singing if the choreo did not highlight who it was. No more, because Seungmin developed a strong presence that demands people to look at him when he wants them to, and keep their eyes on him. It's looming, magnetic and seemingly unexplainable because he really isn't that "loud" with his body, but the audience would still feel pulled into looking. When he's in front, Seungmin has to give life to the words he's singing through his own expression, and rather than look like a storyteller with simulated expressions, he has now reached a point where he is immersed inside the story of what he sings as the character itself now.

Overall, Seungmin has grown into such an amazing dancer, and the fact that he developed this much on top of all his vocal training is a feat of excellence in discipline and consistency. I honestly don't see where else he could take his dancing identity besides growing his comfortability with more emotive bodily expressions of the tteokbokki-spine kind, unless he decides to take the Hyunjin-Jeongin route of going absolutely ballistic-joker expressive with their facial expressions and outright furious style.

Seungmin said in his 200823 vlive: "Efforts won't betray you", and he has demonstrated precisely what it means with how he grew as an artist. He's amazing. Seungmin will never cease to amaze me. If there are greater words than just "awesome", "amazing", I would use them.

Anyway, sorry it took me so long, OP. I really had too many thoughts, and honestly I think I could talk more too if anyone were to ask something more specific, but because it's such an open question I just EXPLODED with thoughts I didn't know how to format in a coherent way 😅 I don't know if this is what you wanted to her, but I hope it was satisfactory? OISJFMOSIMS