Thank you everyone for your help.
Walter, thank you for your hint for http://www.macony-design.de/
Where did you buy your 37mm Close-Up Lens?
What area does it cover?
Acer K132/K135 should be really good choice (money vs value). It's very small and light.
I think the only difference between these two beamers is the SD card slot at the K135, right?
Plug and play, especially with the David camera, sounds very reasonable.
Having a DSLR camera for some extra benefit like taking pictures as well
That's the conflict I'm currently fighting with.
I have to see what camera it will be in the end.
I have purchased a new 4k hdmi capture device that plugs into USB3. I will have it in a few days a report back.
Sounds very interesting, waiting for your experiences...
I found this one: StarTech USB3HDCAP Video Grabber USB 3.0, but it's only Full HD.
Or this one: epiphan DVI2USB 3.0 which cost 3,5 times more than the StarTech.