I think it has something to do with the power management on NVIDIA card. When actively using it things are fine, but there will be a stutter when activating Activities or switching workspaces.

I've tried using the triple buffering mutter patch[0] and still was experiencing issues. COSMIC is looking great but I have some weird screen artifacts randomly.

Hyprland is the only environment that hasn't had any performance issues with my 4070 Super.

[0] https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1441

I'm not sure, but I've found a couple of reports at nvidia's linux forum and their github issue tracker. This is with the open source kernel module & wayland. It's possible that X11 with the closed source module works better, but I prefer wayland.