It mainly comes into play on 7/8k games and is regarding muscle memory.

I grew up playing a 7k flash game which had its default controls as SDF SPACE JKL. Everyone told me to switch from that (ie. linear) to something like ZSXDCFV instead. (ie. staggered) Had I listened, it would’ve been a whole lot easier to switch to actual Beatmania IIDX due to the similar muscle memory. Staggered has LThumb, LMiddle, LIndex, RIndex, RThumb, RMiddle and RRing/RPinky as the main layout. (This is due to needing the left part of the left hand for scratching.)

For 4k, your layout is fine. As for games, there is always Stepmania which has a lot of KB-only charts too. Main version I’d recommend for Keyboard play is Eternia Online.