I know this is more hardware related, so please let me know if I should move this post elsewhere.
I built my first server earlier this year, and put buying a UPS on the back burner. Unfortunately for me, this might have already been my biggest mistake since going down this rabbit hole. The rental I’ll be in for at least another 10 months has some questionable wiring (a lot of rooms/outlets wired to the same breaker), which I believe has created some electrical anomalies and possibly killed some of my computer components. The memory on my PC went first, and now the 7-month-old PSU on my server is toast.
Bear in mind, I am not an electrician, so I could be entirely wrong on why this has happened. Regardless, it's time I invest in a UPS. I have searched forums, blogs, YouTube, and cannot find consistent pros and cons for any of the big manufacturers. It seems like APC and CyberPower are the two big consumer grade manufacturers, which is probably what I should be looking at.
I have a APC Back-UPS 1600VA. It powers two desktop PC/Server, a monitor, and router. So far, it gets the job done.
The biggest downside is; battery is not user replaceable, at least it's not straight forward like the other models. If possible, prefer a UPS with the easy battery replacement option.
Despite some of the comments here, I suggest that you don't overthink it; just buy an APC Back-UPS 600VA and be done with it. You have relatively low power requirements. The UPS will provide some surge protection (490J), several minutes of uptime, and a USB connection for automated shutdown.
The 600VA unit is less than $100 USD and replacement batteries are about half that. I've been using several of this same model for years without issue and we have many brown/blackouts being in a rural BC community. The batteries have lasted me 4-5 years.
You can always plan for something more significant down the road, if your hardware or needs change, but this should do fine in the interim.
If you are concerned about the power quality causing damage, you want an online or double-conversion UPS. Those ones don't even bother trying to condition power, they run off the battery all the time.
I don't have a whole lot of experience, but Eaton has been reliable. People also recommend Tripp-Lite and Cyberpower but they've always seemed cheap to me.
APC makes low end offline UPS units, which are cheap garbage.
They also make line interactive and online ups units, which are decidedly not completely garbage.
I pick up line interactive APC units from used locations like eBay, and go buy off label replacement batteries. Haven't had any problems with them so far.
To date, over the last ~10 years of running a homelab, I have used mainly SMT 1500 units, one was a rack mount. I've recently upgraded to an SMX2000. I've replaced batteries, but never a UPS, and never any server components due to power issues. I've run servers ranging from a Dell PE 2950, to a full c6100 chassis, plus several networking devices, including firewalls, routers and PoE switches. Not a single power related issue with any of them.
It doesn't sound like you need a UPS. It sounds like you needed automatic voltage regulator.
It'll condition the power so it's clean, and if it's not clean it'll cut the power off.
Many good UPS's have a voltage regulator built in, but then you have the hassle the battery and everything. Up to you depends on what's easier to find for you locally