A number of responses to your post claim disappointingly low throughput on the Ubiquiti access points. Having just installed one myself, I was also initially disappointed...until I discovered that the default settings limit peak speeds to about 25% of what's possible with these Ubiquity APs.
I have the UAP-AC-Pro model; two configuration changes from the default yielded speeds as fast as any other access point I've encountered: 500+ Mbits up and down, as measured with iperf3 to a (wired) local box.
There may be good reasons for these defaults, but, briefly, the access point is factory set to use 40MHz channel widths for 802.11ac, and to reserve radio bandwidth for a wireless uplink. To resolve:
1) Update the 5GHz radio to use an 80 MHz channel width (really, two channels); this doubles effective throughput. In the Unifi interface, choose your AP from the devices menu, go to Config > Radios > Radio 5G and choose "VHT80" from the dropdown for channel width.
2) Uncheck the "Enable connectivity monitor and wireless uplink" box in the Unifi main "Site" settings panel; this also nearly doubled sustained throughput, though unfortunately it means your access point doesn't check whether it's disconnected from the Internet. (This may or may not be a problem for you. For me, it means my Internet is down, and it's not useful for my AP to know this too.)
I'm posting this in the hopes that it spares a few hours of Googling for someone else who, like me, was initially disappointed by Ubiquiti's access point speeds!