@itch Good day, 

Currently oneMesh is built through wireless between router and oneMesh compatible RE.

For range extender, only RE mode (wireless connect to router) supports oneMesh, AP mode (wired to router) could not use oneMesh.

In AP Mode, most devices could remember the wireless SSID and password and roam between router and AP, but it may have a few secs short cut off when switch the WiFis , not as 'seamless' as a oneMesh. You may do a real test and see if that works for you,

@Solla-topee Thanks very much for your response. In scenario where Router wireless access is on and Range Extenders are on AP mode with all SSID's the same, would roaming be more seamless?

What about in sceanrio with Router wireless access off and instead using Deco X20's in AP mode connected via Ethernet, will this be a more efficient wireless network?

Thanks again in adance!

@itch Good day, 

In scenario where Router wireless access is on and Range Extenders are on AP mode with all SSID's the same, would roaming be more seamless?

- As AP mode does not support oneMesh, change to the same ssids could not make it more 'seamless' . You could consider a Wi-Fi range extender if your main purpose is to extend Wi-Fi in a certain area, and you could accept a few seconds cut- off when devices roam from router to AP (extender).

What about in sceanrio with Router wireless access off and instead using Deco X20's in AP mode connected via Ethernet, will this be a more efficient wireless network?

- Router -- Deco (AP) --- Deco 2(AP)--Deco3 (AP3 ), in this scenario, Decos are in a 'seamless'  network. You could consider this if your mobile devices need to move around every often, or you have multiple rooms. As you can add more Deco nodes in different rooms. Deco use Deco app for management, please check here for more details

TP-Link OneMesh™ VS Deco Mesh: What's the Difference?

https://community.tp-link.com/en/home/forum/topic/201282