What is your subscription speed and how big is your house.

if you don't mind, top a little get deco m4 (around 360). I can get decent coverage over my double storey house.

I'm not sure, I've not use it before. The result of using powerline can be different due to the condition of wiring and interference etc.

Powerline adapter only work for same phase electric wiring. For 3 floor I would still recommend you go for mesh solution, 1 in ground floor and second one in second or 3rd floor. Pull a wire from the main router to the mesh nodes, and you can still get a decent speed in 3rd floor.

In ur case, mesh is the best option
Just saying that connecting them wirelessly

You will still end up maybe 20-50mbps on 3rd floor but at least you get the strong wifi signal, just the speed wont be  maximum

To achieve maximum speed, pull ethernet cable from ground floor ,connect from router to first unit of the mesh unit, then connect another ethernet cable from 1st mesh unit to 2nd mesh unit,
Use ethernet cable to connect them for ethernet backhaul will allow u get maximum speed anywhere in ur 3 storey house as long u got strongsignal

If pulling ethernet cable is not an option, you can connect them wirelessly, signal coverage is still same but speedwill drop significantly.