Big Sur on Mid-2015 15" MacBook Pro - WindowServer process running amok

After upgrading to Big Sur I noticed that my MacBook Pro would start running its fans while it was sleeping. Also whenever I open certain apps (parallels, certain websites in safari etc) it would make the entire system an unresponsive molasses slow mess, which can only be recovered by a hard reboot.

Looking at activity monitor (when I can) it seems as if the WindowServer process is running at very high CPU utilization, which is often followed by the dreaded KernalTask 700% CPU usage spikes. My suspicion is that this happens whenever the discrete GPU on my laptop kicks in (but I am by no means sure of that) which might indicate driver issues?

Has anyone else had similar issues? Is there any resolution?