X55 access point help

I was hoping for some clarity on this system. This is not my forte but am trying to learn as much as possible as I just found out about this mesh system for my new internet system and gaming.

I setup 3 x55s in access point mode and currently have 2 wifi signals, one off the deco and one off my router. Is that a problem? I thought the deco system would just work with my router wifi but it has its own signal so im not sure if I can use both or if I do all my internet traffic through the deco system.

Is 3 x55s overkill and creating a wifi issue with 2000sqft? Would I be better off using 2?

I read i should turned off smart DHCP while in access point and using my ISP router. Is there any other config I should do to help keep things smooth? Can I change IPv4 to IPv6?

This is my first time doing something like this. Any help would be greatly appreciated. Ill also list my setup and see if anything needs to be adjusted.

My setup is as follows, I have my ISP modem connected to the provided router setup in the basement with all my coax that run throughout the house. I have three ethernet cables running from the router to 3 MoCA adapters that run to three different rooms (main floor living room which is a far corner, far corner room upstairs right above the living room, and another bed room on the other side of the house on the 2md floor). I have then the MoCA adapter in each room and a ethernet connected to the three decos. The main unit is the first floor deco. My house is 2000sqft.