The following details might not be relevant to the problem / fix of slow and glitchy mac dock / graphical performance, but it shows my experience:
Yesterday I was on macOS Catalina. I use LogMeIn Pro all the time to connect to my Windows 7 work computer from my MacBook Pro (16-inch, 2019) laptop. Last night I launched the LMI client (the "latest" version 4.1.7664 (PlugIn: 1.0.2725) ) to do some work, and everything started to seem very glitchy and slow after I initiated Remote Control of my work computer. SUPER ANNOYING!
I decided to finally upgrade macOS to Big Sur in hopes of fixing this problem I was experiencing. Upgrading did not fix the problem. I even tried uninstalling the Client both manually (removing all the necessary folders via Terminal) and automatically using AppCleaner, and a mixture of both LOL. Every time I would reboot my laptop and then re-install LogMeIn Client to see if it fixed it, but I kept experiencing the same issues. I finally tried something different that actually seems to work - and I'm not sure why?...
It seems that launching the client via the "LogMeIn Client.app" app is what makes everything slow once Remote Control is initiated - it needs to be launched a different way:
TO FIX THIS, LAUNCH THE APP THIS WAY:
Locate the app in Finder within your Applications folder
Right-click (or control-click / two-finger-click) it to show the context menu
Select "Show Package Contents"
Open the "Contents" folder, then open the "MacOS" folder
Open the "LogMeIn Client" file that appears there (it is a Unix Executable, so it will open Terminal and then start LogMeIn Client automatically)
Now after I initiate Remote Control to my work computer, everything works wonderfully and glitch-free! I'm not sure at the moment why this works, but I'm fine doing this until there is an official explanation and fix.
Note: Closing the Terminal window will kill the LMI Client process and close it out "unexpectedly"