I experienced delays in Excel whenever I would copy/paste some cells, like this:

A delay of 1 to several seconds was clearly noticeable and inconvenient.

I started to review what had recently changed on my Windows computer. Turns out this was caused by a printer setting: I had recently set a default printer (a network printer), and whenever that printer was not online, I would experience the delay.

I removed that setting and no longer have the copy/paste delay.