However, if you are careful, you can install both P96 and CGX and to switch from CGX to P96 or vice versa, move the used monitor driver to devs/dosdrivers and the unused to storage/monitors, then reboot. You might also need to rename some libraries.
I have this kind of setup, but I prefer to use another boot partition, that has a clean install to test purposes. So, main boot P96, alternate CGX4 (for iFusion for example...)