Just wondering what split sounds do you all use when playing styles ?

Depends on the fingering mode. Which, in turn, depends on the chords in the song, and especially whether there are any slash chords. Somewhere between F#3 and C4 (counting C2 as the lowest note on a 61-key board.)

Note that Yamahas define the split point as the HIGHEST note in the accomp section; Rolands define it as the first/lowest note of the Upper part.

I like Ab2

Ditto!

Depends on the song and how busy my right hand is. If using lower 3, a higher LF octave will make for better strings, etc