@a6ff0b2b While listening to @c713ed05 tonight I took the challenge. On an M1 Max MacBook Pro I opened 300 blank TextEdit windows before I started noticing some perceptible, but not egregious, lag.  At 803 windows Window Server was using 7.56 GB of RAM (TextEdit ≈ 900MB) and was maxing out at least 1 CPU cores at all times.  The entire machine was lagging and moving windows was extremely jumpy. 

 @731bb49a Did you have more than one user logged in?