BV20 lathe use AC bearings for spindle (with 15 deg angle), BV30 should not be different (except bearing size)
I would not touch the spindle for a phase I, gearbox allow full power at all speed, with VFD it is proportional to speed when going lower and constant when going higher, so be ready to throw kW here. I have 1.1kW on VFD for my BV20, and I wouldn't drop gearbox, not enough power for 42CD4 steel cuts or large cut in Al.