A UPS is generally going to provide the most reliable power, but you're going to need a pretty substantial one for each system, and don't expect it to give you more than a minute or two of run time at full load. If you expand beyond 2 GPU/machine, you'll need to look at datacenter-grade UPS systems.
A ups will be a big added cost , i am thinking that a ups is a stablizer with a battery so i don't need the backup power i just want to protect the machines when power goes and return aggressive voltage
Yes, UPS is additional cost but will temporarily address your problem regarding blackouts.
For long-term investment, you might think of solar panel system & now you can say that this system will give you the most reliable power.