I can't comment on your choice of machine - my experience was only converting a Sieg. My one comment on that experience is to research the spindle controller electronics to work out how easy that will be to adapt.

If you're buying a machine to convert to CNC - plenty of reasons why to do this but the question needs to be asked why you don't buy a CNC milling machine from the outset? No criticism, but just that this is the perfect time for you to consider that.

Breakout?, you won't go far wrong with the AXBB if you're happy using UCCNC.

Servos?, cheaper to use Steppers, but with less performance. Just curious?