I'm an IT guy. And I can tell you that computers can make a difference with regards to audio quality. But ..not in the way you think. In terms of audible noise from databuses; no, you won't hear it. Cross talk is an audio spec, not a computer spec.
However, very cheap power supplies from China (under 30 bucks) may cause performance drops in general computing as they are seriously inferior.
As you hinted at, the quality of electricity from your outlet can make a difference. This is especially true with high-end audio gear.
Doesn't mean you need an expensive multi-thousand dollar computer to use for music. Small ITX computers are the best for this purpose as they are quiet and don't generate much heat. This is purely for your convenience. If the power supply is external, that is an ideal option for audio. And...digital audio doesn't use a lot of power on modern computers away.
Laptops and desktops are fine too - but go for something with a solid state drive (nvme or SATA 3 SSD). Skip hard drives, as you don't want to experience latency with larger files. (seek time).
Regarding inteface - if you're using USB, then you need an ifi isilencer USB dongle. This will correct timing errors between the DAC and your computer. Also, get yourself a TRIPP LITE USB b cable with ferrite chokes on both sides from amazon.
Buy a power conditioner. Again, doesn't have to be expensive. I'm using a Monster Power - 8 outlet Platinum with active protection and power filtration. Don't trust cheap power bars with your audio equipment or computer...as they provide absolutely no protection to your equipment.