Then again... could ofcourse then also anydesk to each of them to change whatever they are showing.
For remote control just serve a simple iframe + javascript to poll for changes.
PS: Nice idea, seems like something you would see in a stereotypical hacker movie :)
Depending on your host OS, there _may_ be a way to create more displays that don't require physical video ports, but that doesn't seem to be documented or supported here.
Edit: OH! It's discussed here: https://github.com/pavlobu/deskreen/discussions/86
If "whatever is cheap" is what you are after a couple <$300 4k TVs will probably be better quality, cheaper, and easier to set up than 25 tablets.
Until there is a bullet proof way of creating virtual displays, Deskreen isn't of much use to someone with my use case. Which is a damn shame. I really wanted to use an iPad as 2nd screen.