Bandori has its roots very very very directly inspired from Idolmaster, specifically Julia from Million Live who is voiced by Aimi and plays guitar live on stage while singing. Like, to the point that a specific performance of a Julia song literally kickstarted the planning for Bandori with Aimi as its star. Kidani (president of Bushiroad) and Aimi (who of course voices Kasumi) themselves have confirmed this many times over the years. If Bandori takes any inspiration from Love Live's practices, that's not something I'm aware of.
I also think people don't bring up Love Live because it's an idol franchise, not a musical instrument one, and Kidani is very pedantic about the fact that Bandori is not an idol franchise. (Idolmaster is an idol franchise too, but Julia specifically does play an instrument on stage, which is why it stood out and made the lightbulb turn on for Bushiroad)