@Vincent-TP 

Thanks for your reply Vincent. Can you help me with the following:

1.  Should it be possible to configure my powerline adapter (tp-link TL-WPA8631P) so that it will work seamlessly with my Eero router?  If so, then this is my preferred option as I am getting > 100Mbps with it and I won't need to buy an access point.  

2.  If option 1 doesn't work, with regards to EAP225 (the indoor ceiling-mounted version, not the outdoor) is the supplied POE injector powerful enough to transmit > 100Mbps or would I be better off using a POE switch?

Edited to add - I think I have found my answer to Q.1 - the Eero router does not support EasyMesh or OneMesh.  Is this why I cannot get them to work seamlessly?

Hi  @Hashi101 

The roam I mentioned before is just roaming, not fast roaming. It won't work as well as seamless roaming.

Only with the Eero Ero router and WPA8631P, if you are seeking for fast roaming, you can't do it.

Currently, TP-Link devices can only seamless roam with TP-Link devices.

TL-WA8631P V4 supports easy mesh with TP-Link easy mesh routers.  it seems the most economical way is to change the router.

Please have a look at the easymesh compatibility list.