Well, I have a sort of answer. The TP-link Archer C& (AC1750) I've been using as a hotspot in the sitting room and extension is faulty. Amazon had a deal of sorts so I went for a TP-link AX5400 which is supposed to be quite good. So how good is it? My guess, based on using 802.11AC clients is that it's roughly equivalent to a rather nice TP-link AC1900 hotspot (RE550) that we have upstairs.
This is interesting:
https://www.duckware.com/tech/wifi-in-the-us.html