UPS recommendations for 27-inch iMac 5K

There was supposed to be a Point 5:

5—Look up the power demands for devices you will attach and buy accordingly. A 27-inch 5K iMac can draw up to 295W at max and 75W at idle. Other than laser printers, most peripherals (ink jet printers; external drives and docks; modem/routers) have rather modest power demands

I'll add that not everyone needs a UPS. Macs have always survived power outages better the the competition, and some regions have very stable power. I use them because (a) my iMac makes money for me and (b) I live in an area that can get high winter winds and wild-land fires in summer that make outrages more common.

From long experience, both in workplace and home settings, I only use APC and Tripp Lite power management products.

Some points. I've observed:

1. Almost all UPS units come with both UPS sockets and regular one. The latter are protected but not backed up like the UPS sockets. Be sure to get the right mix of outlets that you need now and in the future.
2. Don't install the software that comes with the UPS. It is not needed in my experience.
3. Neither is a USB connection with the computer needed.
4. Do not attach laser printers to the UPS, not even to the non-backup sockets. I find lasers need to go directly to the wall socket.

For sure you will be plugging in other items such as your Time Machine backup External Hard Disk. However are you looking for brands or specific models.

Finally, we honestly cannot recommend more than brands because you (and only you) know more about what your needs are. Such as what functionality you want out the UPS, how many watts, how much runtime after power goes down, etc....