As you're using steppers, the 200kHz limit shouldn't be an issue. I believe that could be a problem for servos though.

Lets say, 1.8 degree per step, 8x microstepping -> 1600 steps/rev -> 26.6k steps/second/1000rpm (equivalent to 26.6kHz @ 1000rpm). So, below 7.4k RPM at 8x microstepping you're golden.

I use a UC300eth + UB1 for a 3axis + Dual stepper on one axis. Works well but honestly overkill (I wanted the expandability for future 4th axis etc). If you're not interested in the 4th axis stuff, have a look at the AXBB-E (technically, it can do 6 axis but its default breakout is for 4). https://www.cncdrive.com/AXBB.html

Dual Homing in UCCNC is pretty straight forward, just need a limit switch on each side.