I am also NOT an expert on UPS technology, except to know that most inexpensive UPS systems used “stepped” sine waves, which works. . . But is not the best. The APC “Smart UPS” line use something that is probably not a true sine wave, but is really close. I use the Smart UPS line on my 3D printers and SO3, but the regular UPS line on my TV, stereo, XBOX. . .
Here is a post of me running my SO3 and router on my APC UPS and just pulling the plug on the UPS. The Shapeoko doesn’t even notice it.