I am using an Asus router downstairs and upstairs I am using a tp link powerline adapter. When setup there are seperwte networks instead of it being combined into one network. I read about the one mesh system but my asus router supports airmesh instead. So does this mean i cannot combine the networks into one?

If so then how can I make my phone automatically change to thr stronger WiFi connection when going up stairs ? Now it just stays on the downstairs slower connection