I have some queries regarding OneMesh. I do it through Archer C6

and RE200. Please answer my queries on 2 scenarios:

Scenario 1:

When I turn on OneMesh i see that in the app the SSID and password becomes same in both router and extender. And I have successfully done seamless roaming inside home.

But the same successful seamless roaming still happens if i turn off OneMesh and keep both router and extender's SSID and password same.

So where is the difference between them? OneMesh Vs Same SSID. In fact there is a better side, I can connect them through ethernet, but OneMesh is not ethernet backhaul supported. So please tell where is the difference/advantage in OneMesh vs Same SSID.

Scenario 2:

I want to connect 3 or 4 extenders. I know TP Link suggest not to connect more than 2 extender or else i will have poor wifi connection. But i am not worried about wifi strength in this scenario.

(OneMesh turned off) I know that if I make all 3/4 extenders same SSIDs & passwords, they will have seamless roaming, but if there is power shortage and all the devices restart. But the main router restarts a little bit late for some reason, then all the extenders would connect with each other resulting in no internet, even if the main router connects and comes online later.

Now my main question comes here for OneMesh. Will it happen the same for 3/4 extenders if OneMesh is turned on? Also please suggest me, can we connect Extender to Extender to Extender and create OneMesh? And as I have asked, if during OneMesh there is a power shortage and extenders come back online will it start connecting randomly or connect in systematic manner till the router turns on? And so should the internet come back? Is there any chance during OneMesh for the range extenders just to connect to each other but not connecting to the main router?

Thanks and will be highly appreciated if you could clarify me on my whole concept.