Thanks for that information packed reply. I have now tested both powerline and wifi from the router placed in the main house. The powerline worked and luckily also the wifi.
I could only test the internet speed at the different setup and points. I hade 70 Mbit at the 4G router. And similar...
So I am looking to add wifi and mobile broadband internet to the summer house. I am looking for a router to provide the wireless network, it will get a 4g modem into the WAN port.
The house is maybe 80 Sq meters and 4 rooms. It is fairly thin drywall as inner walls and wooden clad outer walls...
Thanks for the information, it is interesting that it would work like that. I already bought the TUF Ax-3000 V2 and not looking to fiddle that much with it.