When compiling code on a remote machine, a terminal on one window would cause YouTube videos to lag on the other! As far as I could ascertain, there was simply no hardware accelerated playback going on. Both Chrome and Firefox had seemingly abandoned X11 for a Vulkan based render backend on Wayland
After leaving KDE 5 to "marinate" overnight (I use Gentoo, so compiling an entire desktop environment like KDE can be time consuming) everything "just worked"
I miss the visual simplicity of XFCE and I'm hopeful to return to it one day, but in the interim, responsiveness is key