OpenWRT on a router without Wi-Fi: what collectd will capture?

Maybe a stupid question but I’m just curious to know what data the collectd plug-in can capture if there’s an external Wi-Fi router. Explaining:

Router like R4S nanoPI with WAN an collectd plug-in
Wireless router with OEM firmware

I’m using Grafana to get lots of stats and alert (here an example under “R7800 router + OpenWRT + tasty stats”), which data I will be unable to get/load? Surely the Wi-Fi speed I think, also the connected clients, what else?

I just wonder to understand how the setup of a wired router + wireless router will work!