Yep. My "TV" upstairs is just a giant LED computer monitor with two HDMI inputs and my "TV" downstairs is a projector -- both connected to old laptops.
I've read digital signage is the way to go for bigger screens, though I haven't looked into any recently.
YMMV, but I've never had a microwave interfere with my 2.4 GHz wireless.
Microwave ovens are literally Faraday cages tuned to contain/block signals in the 2.4 GHz range. If any are escaping while it's in operation, then there's probably a problem with the shielding (either damage or poor design).
One way to test is to enable wifi on your phone, put it in the microwave (obviously do not turn the microwave on lol), close the door, and the wifi signal should disappear (assuming it doesn't fall back to 5 GHz).