Easy Dumb AP - like with Fritz


I am pretty new with OpenWRT, so I am sorry if the question was already asked, but since I do not know the right terminology, it is hard to find an answer.
I am coming from the Fritz Routers and have a 6430 (provided from ISP) and 7362 SL hooked up together in "mesh". I would have to use the 6430 as a modem, but span a new Network with my Redmi AC2100 (OpenWRT) and Mi WiFi R3 (X-WRT).
I already figured it out, that my R3 should be used as a dumb ap, but I was wondering if there is some way to just apply the settings of my AC2100. If I want to change some settings regarding the network, it would be quite awesome to do it only at one point and not copy paste the changes to other APs.
If you have any other tips on how I can achieve this, I would be grateful!

Thanks in advance.