I believe the UDM has what amounts to a Unifi nanoHD AP in it, so presumably the range would be comparable, taking into account though where you would be placing the UDM.Right... how is the 5GHz range on the UDM vs say an R7800? They may make it so so and just recommend adding switches and access points?
For instance, I would put the UDM or UDM Pro in a closet with my other networking gear, so would expect loss of WiFi range if I go with UDM compared to my nanoHD which is mounted high on a wall - with fantastic range.