Pulley for 10 Gear Derailleur for 9 Gear Chain
Changing your pulley/jockey wheel to a higher/lower tooth count will not change the shift indexing of your derailleur, it'll only change the tension of the chain. (if you replace an 11 tooth jockey wheel with a 16 tooth, you might wanna add a few links on your chain)

Changing jockey wheels shouldn't matter for as long it has no conflict with the cage of the derailleur (the plate thing holding the jockey wheels), either being too large to fit or having incompatible axle-bearing contact/diameter (very rare though).

I'd recommend having narrow-wide jockey wheels especially if your derailleur doesn't have a clutch. There's a reason why SRAM adds it on their derailleurs and roadies/CX riders like it. 

Also, no need for sealed-bearing wheels. Jockey wheels with bushings are sufficient especially if you plan to replace them every 6 months.