yes
2.4ghz better than my old router asus N12U
old about 2 or 3 bar from 4, now 4 bar consistently. (2 wall)
if but 5ghz got problem if got wall(only 2 bar from 4)

well its simultaneously 2 band router. so no problem because both band is active

its should be same.
i just buy it and then flash it, i didnt use as stock router

It is better from my perspective with Padavan
More stable in every aspect especially on wifi and functions while give option to support for unifi vlan tagging and VPN server.
It also allow to work as 5gz repeater which default Xiaomi only repeat at 2.4ghz.

Only disadvantage from me is does not support QOS.