Question about NZXT H9 Elite All white

Should be, mine is bigger and fits, the holes for the screws are univsersal

should, I have the phatek 1000s in it:

Phanteks AMP v2 80 PLUS Gold power supply, modular, PCIe 5.0 - 1000 watts, white

also fits in terms of colour ;-)

Yes, have temporarily installed an RM750 and it fits perfectly