I'll try and answer these for you...
1.The PSR-3000 will allow up to 32 bars in each style section...the more bars used,the larger the style size will become and it will take up more space in the user/card storage area.
2.The Style Creator is onboard the PSR-3000.I use it to take parts from one style and use them in another(Assembly)which is the easiest form of editing but still will give great results.
3."Groove & Dynamics will change a swing to an 8 beat,or an 8 beat to a swing.You can change 8 beat to 16 beat.You can change an English Waltz to a Swing Waltz.
Groove & Dynamics can affect one style part or any number of parts.
4.Styles can be from approximately 12 KB(a basic piano style) to 32 KB or larger,depending on the number of parts used and their complexity.

I hope this helps.

Ian