Main question: Has anyone found a reliable current android app to switch to the strongest AP (same ssid). I find they're very 'sticky', keeping to a weaker signal that's hardly working

More info
My parents have a house that's a nightmare for wifi (metal in the concrete), the answer is cabling but that's out of the question.
They're old and I need to be able to fix things remotely

We currently have

• 2 x TL-PA9020P making a wired link to another room
• TL-WPA8630P (can I confirm this won't work with onemesh)
• Also a netgear Ex7300
   

Problems:

• Sometimes the TL-PA9020P fall over and disconnect. I can't see a way to get them back up remotely. I have have to try some kind of smart socket for this
• TL-WPA8630P - Just seen there's finally a potential fix for this problem https://community.tp-link.com/en/home/forum/topic/172278 but I'm absolutely against furthering it with other devices that suddenly decide they want to be a DHCP server (I run my own). This issue has really dented my confidence in TP-link as the solution.

If I can sort the android switching I'm ok with just putting in more powerline wifi extenders
 

I was also looking at a mesh. The deco 9 is tempting because of the powerline backhaul as but don't like the master/ slave design and I'm not sure if it will handle Fast Roaming (?)

Because of the terrible wifi through the walls I'm not particularly convinced a mesh network will work, though I'd be tempted if it will 'hand off' the devices to the strongest signal (Fast Roaming) better than the current solution.
 

Having the option for ethernet backhaul would be nice, in case I can convince them that cabling is the way to go.

So I kind of feel I'm stuck inbetween two imperfect solutions here.

Any thoughts from someone with experience please?