BGW20 gateway with Orbi router
New to this forum and just got ATT fiber (1gb). After talking with the tech who installed the gateway I decided to update my wifi router to a Netgear Orbi wifi mesh router (wifi6). I've setup the Orbi and things seem to be running fine. But I'm reading something repeatedly about how I need to disable my wifi from the gateway if I use another router (in this case, Orbi). I didn't do that and yet I can still run my Orbi and ATT gateway at the same time. When I run speed tests the ATT gateway is faster than the Orbi but not terribly faster (ATT=900mbps while the Orbi is around 700mbps).
My questions are...
1. Do I really need to turn off my ATT Gateway wi-fi? Seems to be working with the Orbi without trouble as far as i can tell
2. Should my Orbi be as fast as the ATT Gateway? When I run a speed test from the gateway to the Orbi I get around 940mbps but a step down when I connect a device to the Orbi vs BGW20 gateway. Is that expected?
3. I noticed that the ethernet cable is a cat5e, (going from gateway to Orbi), should I upgrade that cable to cat6a? Would that help?
4. What about other wifi routers I have in the house? I have a netgear nighthawk and speed looks pretty good on 5g channel (around 700mbps). I also have a google mesh router in the house. I know that sounds weird to have all these different routers but I got the google one for free and ran all my Nest devices on that network so communication between them is seamless. My plan now that I have the new Orbi was to turn off the other routers but I just never got around to it yet (I have a lot of Nest devices so I was dragging my feet because I would have to reconnect them).
You can probably tell I'm a newbie by my questions so go easy on me when you answer. I would appreciate dummy down for me until I get better acquainted with ATT (came over from Xfinity)
Thanks in advance.