Seems like the WhatEverGreen.kext got updated to fix some of these graphics issues so updating to the latest may work for you. However, all my issues went away when I switched my SMBIOS to iMacPro1,1. MacOS takes advantage of iGPU for rendering on FCPX (as has been explained in this thread) instead of using dGPU. There's something that's incompatible with the FCPX frameworks and our iGPU (even if you have it properly configured for your system). The idea is to bypass the iGPU and just use the dGPU so that your OS doesn't switch between them. If you configure your clover with iMacPro1,1 for example, it will just use dGPU for everything since iMacPros don't have an iGPU. This also fixes Netflix, HBO, prime, etc streaming.
Hope this made sense. Also, keep in mind that changing your SMBIOS on clover will also require a new SN, MOBO Serial, etc. Your iMessage, facetime etc will have to be reset/reactivated as well because it won't work after the change. There's plenty of tutorials online on how to do this.
Try updating whatevergreen first since it is the easiest method and you will have to do this regardless. If still doesn't work move on to switching SMBIOS.