Example :

Ground floor - Main Router

1st floor - mesh router (connected wirelessly to Main Router), can this mesh router connect to a PC with Lan cable?
or
1st floor - mesh router (connected via Lan cable to Main Router) better?

I recalled reading somewhere, that mesh router can be connected to Main Router via both wireless or Lan cable also can right?
& mesh router can be connected to PC/devices via wifi or Lan cable also can, correct?