>Would a Pi Zero W work for this, or do you need a full-size Pi 4?
I tested Key Mime Pi (the keyboard-only version) on the Pi Zero W and it worked great. I haven't tested TinyPilot on the Pi Zero W, but I think it will work. The video encoding is happening in the HDMI dongle, so it doesn't hammer resources much. I don't have a USB to microUSB adaptor on hand, but I'll order one now and see if it works.
>be able to package everything into a tiny 3D printed case.
Yeah, that would be neat! One of the biggest issues I have with TinyPilot's setup right now is that it looks kind of like a bunch of random hobbyist parts stuck together. A 3D printed case would be good and wouldn't have the heat issues that Pi 4 has.[0]
[0] https://www.jeffgeerling.com/blog/2019/best-way-keep-your-co...
The official documentation[0] says all Pi devices have USB OTG, but I'm not sure if there's something else about the Pi 4 and Pi Zero W that allows USB gadget mode because I've never found anyone talking about using it before recent generations of Pi. This StackExchange answer says the A and the A+ had it, but that the 2 doesn't.[1]
[0] https://www.raspberrypi.org/documentation/hardware/raspberry... [1] https://raspberrypi.stackexchange.com/questions/71613/how-to...