Time for a VFD sticky,
RPC sticky seems like RPC's are only option to consider.
Simple things like, 1 ph input to get full power 3 ph, a 1 hp VFD is all thats needed for 1 hp motor if VFD is rated for that power, at 1 ph or 3 ph input, proper shielding of control wiring, basic 3 wire circuit to get a simple remote control up and running, control wiring is all low voltage instead of HV (or control xformer) for RPC's, no switches/fusing/reactors on output power.. direct wires only, where a RPC would be better, calculating speed with VFD, enclosures, reusing original switches, Why not to run a 2 sp motor switch with VFD. A CNC requires an interface to VFD for spindle control. Derating 3 ph input drives for 1 ph input. Fwd/Rvs contactors not needed, Pgm for less whine, VFD provides motor protection/heaters not needed. Input fusing/disconnect/basic E stop. Types of cable needed for install, type of potentiometer.. Light weight and small size of VFD vs RPC.