My 2cents take on this, for 2 story house use case for those who hate pull cable to add new AP
Asus ac55uhp (Around RM499) + tplink powerline with ac1200 dualband (around rm450) = full house coverage suitable for max unifi 50mbps. All devices at different floor can connect to new SSID either 2.4ghz or 5ghz and get almost full capable speed.
This setup isnt that ideal for 100mbps unifi due to limited uplink at powerline linkspeed and house electrical connection.
If go for 1 powerful router like Asus AC86u, bottom floor still needs AP or repeater to efficiently cover blindspots
If go for default unifi AC router, need to pull cable to install another AP
If go for default unifi AC router then add repeater at different floor, network linkspeed will cut to half unless go for those expensive repeater (costs about rm600-800) that bridges on different band and repeat on different band. Result still vary