So you're saying when you press the delete key once, there's a noticable delay between when you press the key and when you see the character on the screen disappear? If so, I have not experienced that outside an entire app being laggy (and in that case it's any keys, not just the delete key). Not even when using a Bluetooth keyboard has that happened for me on my M1 MBA. I'm assuming you've already tried quitting/restarting the apps and also rebooting the computer?