Mesh is great in theory. In practical application it does not always work. It's client dependent. Basically the WIFI radio in your devices needs to be tune-able for roaming otherwise they don't hand off a signal until they lose it.
Meaning you could be sitting on top of a strong access point but remain connected to a weak one and it won't hop until the currently connected one is no longer reachable.
Forget the powerline stuff. Works well on the same circuit. As soon as they go through the panel all bets are off.
If you want to limit hoping / having to switch networks and don't want to drop coin on mesh there is this option.
I use them on my security cameras and they work awesome.
My camera out back is 100 ft away from the receiver and has the signal passes through multiple walls and obstructions that are not WIFI friendly and the signal is as strong as the front door cam that sits 10 ft away from the receiver.
Assuming your current router has external antennae of course.
NOTE, there are 2.4 and 5 versions.
https://www.amazon.com/gp/product/B01B94U438/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1
And the supplied cable is a bit short, I grab one of these at the same time. Makes placing it more flexible.
https://www.amazon.com/gp/product/B01E9V8T62/ref=oh_aui_detailpage_o03_s01?ie=UTF8&psc=1