UPS Should not affect the performance,
In fact I have recommended friends to use them on their main internet equipment and along with myself we are all happy with the continuity of service during a minor power blip.
I use 3 x APC UPS BX500CI APC UPS AMAZON
These run with various requirements
3=Office PBX Telephone exchange
and they work a treat. No usb port on the 500VA Version but that is no issue to me as no need for the communication, whereas the bigger models in that line do have USB ports.
Runtime is approx 20mins on all scenarios.