Using Eeros over MoCA with Xfinity Modem/Router

I set up an Eero network with 3 WIFI nodes using one eero directly connected to an ethernet port on the Xfinity Modem/Router and two other nodes connected using MoCA ethernet adapters that use the MoCA capabilities in the Xfinity router.  Since I want to use the MoCA capabilities in the Xfinity router, I can't set the Xfinity router to bridge mode. 

Should I set the Eero gateway to bridge mode?

The Eero gateway is not in bridge mode and I am seeing behavior I don't understand.  Last night, after setting everything up, nothing seemed to work — I was getting very slow speeds from the Eero WIFI nodes. Some of the nodes showed wireless connections instead of wired backhaul. I was about to return everything. I woke up this morning and everything seemed to be working great — all nodes showed wired with good speeds. I have no idea what changed.

Strangely, the eero gateway and one of the other eero nodes (MoCA connected) show 192.168.4.x ip addresses in the app, but the other eero node (MoCA connected) shows a 10.0.0.x ip address. The former look like ip addresses issued by the eero gateway but the 10.0.0.x ip address looks like it was issued by the Xfinity modem/router. I have no idea why.

Another oddity is that some of the WIFI devices seem to continuously jump between the two MoCA-attached eero nodes (according to the app), as a set. Strange.

I suspect I need to put the eero gateway in bridge mode but I would like to understand what is going on. I suppose an alternative would be to get another MoCA adapter and put everything behind the eero gateway but I'd prefer to avoid the expense.

Any ideas or suggestions?