anon i want you to know you've deeply delighted me with this question. disclaimer that i'm not a tea expert + am not super aware of cultural tea uses/ceremonies! but i did work at a tea shop for a while + have enjoyed tea for many years.
faust: has a tea for everything. starts the day with hot green tea (matcha if he didn't sleep well, for a little extra caffeine). ends the day with an herbal tea suited to whatever the day involved; uses his herb knowledge (medicinal + curse-related herbs) for tea-making, and will make mental notes throughout the day like, "i felt a little congested today, i'd better add x herb to tonight's tea". takes his tea plain, no milk or sugar or anything; will still drink tea even if it's oversteeped or he forgot it and it got cold (though he's not immune to making faces about it).
faust and brad both love lapsang souchong; it smells like a bonfire, which calms faust and reminds him of his mana area, and it reminds brad of his bandit days, roasting meat over a fire and laughing and drinking with his men. this fits extra well considering apparently they have the same favorite alcohol
brad: doesn't really strike me as a tea type, but he's from the north, so i imagine hot beverages are favored... i think he'd opt for plain black tea in the mornings to help wake up, or black tea with fruity flavors
nero: similar to brad, black tea in the mornings, but i think he'd add a little milk and experiment with additions like cinnamon, citrus, etc... in afternoon/evening maybe he'll enjoy a more savory (?) tea like barley tea or genmaicha, except he brews it as he's cooking dinner and then forgets about it and it goes cold. tho i guess he can reheat it with magic. oh and he'll make hot tea with milk for the kids when they can't sleep
leno: he lived in the mountains of southern country and worked alongside figaro, so i imagine he developed a working knowledge of herbs native to the southern mountains. including whether sheep and dogs can eat them lol. he feels like more of a black coffee in the mornings guy to me, so i think he would enjoy a black tea or matcha in the mornings for the caffeine. he drinks it hot when he's in the mountains where it's colder, but he drinks it cold in the manor in central after going for his morning run