I think I understand I must provide focusing hardware (Robofocus?) but I am not sure if I have to provide Auto Focus software (FocusMax)?
If RoboFocus provides ASCOM driver, then that’s all SGP needs. No need to use FocusMax and besides, I do not think SGP can work with FocusMax (works with other software like the very expensive Maxim DL).
Ascom driver of the focuser is all that SGPro need. It needs to comunicate with the focuser.
The focus routine is built into SGP and you don’t need external software to make it happen. The only two program sets that SGP relies on for outside support is guiding (PHD2) and plate solving (Elbrus, Astrometry.net local server, Pinpoint).
You will need ASCOM to communicate with the devices too.