Different (lan x guest) speed wifi - reason?

Foris does not have “country code” , meanwhile Luci does and needs to be set. If left empty and you save+apply the uci config from Luci interface, it might not work properly (or at all).

I think it is better to set the wifi in Luci (and look into “Advanced Options” tab … where is the country-code and some other params you can play with to tune it up, distance, signal level… Foris should handle wireless config saved by Luci. (i do not use Foris unless it is necessary or just for some essential features missing in luci)

Similar issue where Foris and Luci do the changes in UCI configs regardless the other related option “dynamic/static domains” and “port 0 vs port 53” (for resolver/kresd/dnsmasq) it took me a while to found that glitch.