How to connect ATT BGW320-500 to TP-Link AX3000 Deco 60 Mesh Network

I was recently set up with ATT fiber optic 1000 service and the BGW320-500 gateway.  I was able to connect it to my TP-Link AX3000 mesh network (3 satellites/nodes) with no problems.  Speed checks around the house are good (in the 500-700 mbps range).  The tech who set up the ATT service and gateway said I could leave the gateway's wi-fi on as well as connect my mesh network.  I have done that, but it looks like I have two separate networks that way.  I assume that means I have "double NAT" - I'm not totally sure what that means, but my understanding is that can cause problems.  My thinking is that I would like to just use the BGW320 as my modem and convert my TP-Link mesh network to wireless access points. This would allow me to move the TP-Link unit that I'm currently using as my combination modem/node to another area of the house to improve my wi-fi coverage.  My understanding is that I would then essentially have 4 wireless access points including the one on the BGW-320.  Can I accomplish this by just changing my TP-Link system to WAP mode and then rename the BGW320 SSID and change its password to my desired name and password?  I don't use advanced functions like port forwarding (not even sure what that means).  Will my proposed set up work?  I don't want to jeopardize screwing up a setup that currently seems to be working well.  My goal is just to avoid having two networks and gain better wi-fi coverage in my home.

Thanks!