[TorqueDog]

Let me try answering this way.

1. Do you have Comcast cable TV with set-top boxes?
a) If no, you can use bridged mode on the router.
b) If yes, answer #2.

2. Are any of the set-top boxes connecting wirelessly (ie: only power and HDMI cable plugged in)?
a) If no, you can use bridged mode on the router.
b) If yes, do not enable bridged mode on the router. This will disable this wireless ability for those set-top boxes.


Answering your questions:

1. If you use the Decos as access points, the Decos will hand off nicely, the Xfinity probably won't and it'll fall to the client to pick the most suitable access point and you may notice some fussiness there. In that instance, keep your Xfinity network separate, and only use the Deco access point network. I don't know how big your house is, but I've had success setting up large four-storey infills using carefully placed Eero APs and ignoring the Xfinity gateway's wireless entirely.

2. I'm not sure what the flashing indicates, that the connection is successful and consistent end-to-end? How old is the house? If the cabling is too old -- I once worked on a previously reno'd house that had Category-3 cabling and they couldn't understand why none of their interfaces would link above 10Mbit -- then it would make sense why the Decos won't work.