I have AC hardware and run ethernet and routers as switches and WAPs.

I don’t know about AX or mesh networks, but if they both also use the 2.4 and 5 ghz wireless spectrums, your limiting factors are walls and distance. You can only combine two max. So it’s either w+w, w+d, or d+d. Try to add a third, and it’s not going to work.

Your throughput in each floor is about what I expect if you’re trying to push one wireless access point over 5 floors. And that 5mbps isn’t probably a ‘real’ 5mbps. 5mbps you can still game/stream easily over ethernet, but 5mbps from 1gbps over 5 floors via wifi is unplayable and unwatchable. That’s like getting 90% packet loss.

Are your parents messing with your internet connection?