We run a few P20's mostly P25's. Observed same when starting our rollout.
- Pool setting: try disabling 3D (requires it be PCoIP only pool, IIRC)
- VM setting: performance information and tools, adjust visual effects, try "adjust for best performance" and see if that helps. Notably "show window contents while dragging" has a big impact. If adjust for best performance fixes, you can play with turning on individual items if you really need them and see what works in your environment.