Hello, 

I have setup 3 BE-230 routers in a mesh network 1 router being the main and the two other are mesh nodes connected via wired(Ethernet) backhaul. All routers with the latest firmware. 

My isp provider, provides a router, I went into its setting and closed the 5g and 2.4g bands so they are no longer visible. I have also turned into DMZ mode since the isp provider does not allow me to make the router as a bridge only. From what I understood DMZ and bridge should more or less do the same thing, i still have double nate but theoretically since i am sending all the isp routers work to the main BE-230 and everything is connected to the BE-230 it should remove double NAT theoretically.

I also have noticed that my main router when I enter to its settings it is using 43% memory(which I am assuming is the RAM) is that okay or is it high? Should my main router be upgraded?

my question is as follows: my main tp-link router should I set it up as an access point and create mesh that work (i don't know if that works) or should I keep it as it is(router)? 

another question if in router settings is there any other settings I should change to get the best connections. And if in ap or router mode should I change anything else as well for example putting on different channels and close the dhcp so I don't get any conflictions between the tp-link main router and my isp router? Keeping in mind I have closed the 2.4g and 5g bands on the isp router.