GPU memory restriction
If your game is on a SSD but the save files are present on a HDD, it will cause stuttering and CPU/GPU spikes every 5 seconds or so. Move your save files to the SSD or create a symbolic link as described on https://www.reddit.com/r/mirrorsedge/comments/c0ohs2/if_anyone_still_wondering_the_fix_for_me_catalyst/
To automate this, put the following commands into a batch file (.bat extension) in the game's directory and use the .bat file to launch the game (The batch file has to be ran as admin):
wmic process where name="MirrorsEdgeCatalyst.exe" CALL setpriority "high priority"