If you have access to the router, you could probably adjust their device to have random packet loss. Which would effectively slow them down, might piss them off.

As for the deauth attack, it definitely isn’t “easy”. But here’s a tool to do it. github.com/aircrack-ng/mdk4. However I doubt this’ll be interesting to you.

Also, microwave (2.4GHz interference) won’t affect Wifi 5/6, given they’re in the 5+GHz range