VFD, Vari-speed bridgeport best practice

I've got a VFD which I basically use as a phase converter. then set the speed manually with the varispeed on the mill.
I recently replaced the VFD and I'm reworking the configuration to control it with modbus.

Now I'm wondering how people use this in practice. Do you set the varispeed in the middle of the range and then control speed with the VFD? How do you calibrate it?

Or is it better to set the varispeed near the top end?

The motor is a 2HP 1720 RPM skyey.

I have a mill that used to have a varispeed. It also has a gearbox. I replaced the varispeed with a 1:1 V-belt drive so this would correspond to you setting your varispeed in the middle.
If you have spindle feedback of the actual spindle speed you could do fancy stuff like automatically calculate the ratio of commanded to actual speed and compensate the commanded speed accordingly.