I have similar experience but then I just noticed on the activity monitor and saw the red text 'CursorUlViewService (Not Responding)' and tried to kill the task and saw the improvement. It is a glitch with the recent os and with the archicad software only.

Look for this CursorUIViewservice (Not Responding) on your Activity Monitor and kill the task then it will resume to it speed when typing. This is a glitch on the new os of the mac and keep on coming back so I have my Activity Monitor on my side and cross (kill) the task whe...