Thanks Matt! That all sounds very solid and exciting! I've looked and saw that there's even a UniFi 3-pack bundle for about 250 euro. This is a good price, and I'm guessing I don't need more than 3 AP's anyway. I don't really need AC speeds either since most of my WiFi use is just surfing the net with a bunch of different devices (2 iPads, 2 iPhones, 1 laptop). I'll also have a look at those RouterOS routers, but I fear they'll be hard to come by in Belgium.

I also recognize what you mean with the modem/routers most ISP install nowadays. They do this here too, but I was able to persuade them to give me a modem only install instead of the modem/router because I told them I use VOIP a lot and I knew that this was problematic with their modem/routers. This wasn't true, but I really did not want one of those modem/routers because they allow the ISP to login from remote into them (and so I'm guessing also your LAN if they really wanted to) and they make your setup part of their nationwide network of free WiFi hotspots (no, thank you).