Question Good UPS (price/quality) for Corsair CX450 PSU

[fastshot]

Due to brownouts and blackouts I've to get a UPS for my desktop PC.
My PC has got a basic hw configuration so it need a low power to work, I mean about 150-200W max everything included, and I need a UPS that will work only for the time to shut my system down during blackouts, I mean 1 minute or so. Anyway I've to be sure my hw will be safe during brownouts, which are quite common (2-3 times per day), especially my mechanical WD black @7400rpm (WD1003FZEX-00K3CA0) hard disk.
My PSU is a Corsair CX450 (CWT manufacturer) and I'd like to spend the lowest budget to get a UPS that works fine for my goals written above.
First of all I don't know if a pure sine wave (PSW) is necessary for my personal case/goals or not and I ask you that because this will mean a lot of money of difference. I just know my corsair is PFC active if this is an important difference.

Cyberpower is a middle-range UPS brand here in Europe so I've pointed to
https://www.cyberpower.com/eu/en/product/sku/cp900epfclcd
VA 900 - Watts 540 (Output Power Factor 0.60) - Line-interactive UPS Topology - Active PFC Compatible - Pure Sine Wave Output
and this is my "milestone" both as specs and budget for now. Consider I can get it for about 170eur (shipped)

BlueWalker's Powerwalker is another very very cheap alternative here:
https://powerwalker.com/?page=select&cat=VI_SW&lang=en
and the closest to the above cyperpower is
https://powerwalker.com/?page=product&item=10120080&lang=en
800 VA - 480W (Output Power Factor 0.60) - Line-Interactive - Active PFC - Pure Sine Wave
I can get it for 85eur (shipped).

By the way I didn't understand if the PSW they both claim to generate is ONLY during the blackout (when the UPS does its "hard" job) or is always. Can you explain?
Now let's consider the money you spend in perspective, in other words: how much time will they last? The cyberpower costs the double but will it last the double or much more (or the same)? Let's include the batteries cost within this calculus of course. Finally let's consider what I will fix myself with my tin welder (eg. capacitors and other "easy" stuff) because I guess a cheaper UPS will carry cheaper components. Well now... tell me your answer

Thanks in advance for you explanations and suggestions

 

[tennis2]

Just looking at the Cyberpower unit:
https://www.cyberpower.com/eu/en/product/sku/cp900epfclcd#specification

https://www.cyberpower.com/eu/en/product/sku/cp900epfclcd#runtime_chart

Runtime at 200W = 13minutes, Typical Charge Time = 8 hours.
Obviously the battery won't begin recharging until power is restored. Sounds like the PC isn't on while you're asleep, so the UPS will be fully charged at the beginning of each day (from recharging overnight)

Based on your estimated power draw from the wall, desired runtime per event, and event frequency WHILE YOUR PC IS ON, you can determine what you need.

Past that, you're talking about quality, features, etc when comparing different brands/models.

 

[fastshot]

Sounds like the PC isn't on while you're asleep

Yes, my PC isn't.

event frequency WHILE YOUR PC IS ON

At least 1 brownout per day for sure. Blackouts event frequency depends on rainy days: if it rains hardly blackouts occur for sure, I guess it depends on a shorcircuit never previously found on my "new home" electrical system... now it's cheaper for me to get an UPS than paying a professional to solve this trouble for me
I think I've already answered the other questions, so... will I need a PSW UPS or a simulated sine wave one is enough for my cfg and goals?