I'm getting a new FTTP connection
Old single story stone cottage with internal stone walls

I'm considering using TP-Link Archer AX1800 Router, plus a TP-Link RE600X AX1800 Wi-Fi 6 Range Extender.

Both to be in the attic which has a single stone wall, with each on one side of the wall
Th wall has a small access hole through it.
Idea is to connect the Router to the Range Extender by ethernet cable through the hole.

I've looked at manuals for both of the products and can find no reference to connecting this way.

Question is, can this be done and if so are there any settings I would have to change?

Also since the Wi-Fi is required in the rooms below them should their aerials be set horizontally rather than vertically.

Appreciate any advice.

Thanks