26 Clients is about the maximum i would recommend for any router, but yeah it should work. You might experience some dropped packets here and there, but if your software is good enough they should be no problems.
I would however not go for the cheapest GL routers, go for a newer one such as the S1300, AR750s that have 5ghz wifi for your pc, and for any future upgradability.
Expressif have been teasing a new IC called “Chip 7” which is rumored to have 5ghz wifi.
Sure but in a regular household all the devices might not be on at the same time, or transmitting at the same time.
Since your devices will be on and transmitting constantly, that is another story.
The S1300 can probably handle 50 clients since it has a faster cpu and is dual core, but the AR750s can probably do around 30 max, so i rounded down a little.
Usually if you have a lot of clients on 1 room, such as some kind of event, you usually have multiple AP’s running at lower power so that they barely overlap, to handle all the clients. So you would have something like 6 or 7 AP’s for 300 clients in one room.