I'm again trying to help my next door neighbor with his working home network.

As described in my previous post back on 4/16/23 (3-node Deco M5 mesh configuration behind T-Mobile Home Internet Gateway) he has been using the Deco M5 mesh network for the past 10 months with cellular internet service via a T-Mobile Home Internet Gateway, but has been very disappointed with the T-Mobile service in terms of reliability and bandwidth. We are in a fringe LTE/5G service area for T-Mobile and he does a lot of 4K TV content streaming and I think his bandwidth is constantly being de-prioritized and occasionally reverted to LTE service.

His dissatisfaction with T-Mobile's internet motivated him to order a Verizon Home Internet gateway on a 30-day money-back trial which he asked me to install.  Back in April when I installed his T-Mobile gateway and configured his tp-link Deco mesh network, I disabled the T-Mobile gateway's WiFi and configured the Deco mesh in router mode using a wired ethernet backhaul between the gateway and mesh nodes.

I was wondering if I should simply disconnect the wired link between the T-Mobile gateway and 1st Deco node, and then reconnect the 1st Deco node to the Verizon gateway.  But before reconnecting the Deco mesh to the new Verizon gateway, should I connect my laptop beforehand to rename the gateway, see what kind of signal he gets from Verizon, and do anything else?

Thanks for any suggestions and guidance.