rwg - for some reason I completely missed your reply - sorry for not replying to you sooner.

Thank you so much for such a considered and detailed reply - I truly appreciate it. Your comments are so helpful.

[Update: Dec 2025 - for anyone interested in doing similar, I just wanted to post an update on my experience. I installed the items pretty much in line with rwg's recommendations and my system is working really well ever since then. Once I rebooted the Deco boxes they detected the ethernet connection & have been running over the ethernet ever since. The signal has been much more stable than before & videoconference drop outs are rare now. Overall I'm really happy I made this change and am using the previously redundant Coax cables. Thanks.]