Hello!
I have currently a site with OpenWRT Router (Raspi 4) and Unifi APs (4 U6 Lite and 2 old UAPs), with a smart switch and a dumb switch (both TP link), Unifi controller on Raspi4 as docker. Three VLANs with three SSIDs: two for guests with different policies, and one for myself.
I am getting suspicious of Unifi for some reasons (the most grave one is, I have a feeling that Mac airs are not getting IP address always, and that it's partially because of unifi, though Mac airs also seem to have problems), now I am preparing for a new site, and after some research, it looks like TP-Link EAP 225 or 245 seem to be a good option in terms of price, performance, and manageability for myself. I would be running about 9 APs there (the size of the building is about the same as the first one, and will have fewer clients: about at most 15 devices, about 5-6 people). Probably just two SSIDs, both guests but slightly different policies.
It's just that I have no other experience than what I have now with unifi, and I heard that there are things like xx AP and yy router don't work together. I would appreciate if someone could tell me something about it. For OpenWRT router, I don't plan to use Raspi: I will use Frizbox4020 which I already have, or buy something else. (may be Archer C7). I will get Telekom VDSL50 or 100. For a controller, I would probably get OC200 Controller: it's pretty inexpensive.
Also I would appreciate advice in choosing 225 or 245 though it's off topic here: I live in Germany where EIRP is limited to 20dBm for 2G, and would like to have about the same coverage as I would get with Tx Power 17 dBm. If the antenna gain is more, Tx Power has to be less, but I am not sure if the antenna gain is going to compensate well in terms of connection, even if RSSI may be lower. EAP225 is cheaper than 245 but has more antenna gain, so I worry that Tx Power might be then too weak.