How I solved my particular input lag,floaty mouse,desync, degraded visuals problem

[1nputlag34]

3-4V should be within a limits where you should not see any PC symtpoms, the problems became noticable if it drifts to 5V or higher

Yes and no it really should be 0 when you turn off the entire circuit breaker panel, because that rules out any devices plugged in at our end. If you measure even a few volts, it proves there’s a problem upstream of the circuit breaker panel. I’m not saying that those few volts cause input lag on the PC, but that it’s one of the symptoms of an electrical problem maybe a high-impedance neutral, a floating neutral, a bad resistive contact, oxidation, or something else that’s causing the input lag.

[MK92]

It is impossible to have 0V with shared neutrals on an old TN-C installation, if those 0.5V would case problems, then literally 30% of all people in Europe would have those problems and it would be impossible to use computers in any building older than 1985.

I had 5+V drift during the day, and even up to 8-9V right after I turned off induction hob and ironing and oven, and now it still about 1-2V during the day but I don't have any problems.

[1nputlag34]

It is impossible to have 0V with shared neutrals on an old TN-C installation, if those 0.5V would case problems, then literally 30% of all people in Europe would have those problems and it would be impossible to use computers in any building older than 1985.

I had 5+V drift during the day, and even up to 8-9V right after I turned off induction hob and ironing and oven, and now it still about 1-2V during the day but I don't have any problems.

I didn't say it's a problem, but that it's a symptom. If there's voltage between ground and neutral, it's probably coming from the appliances in your home. If that's not the case, it could be a sign of a bigger problem.

Try turning off all the power in your home and measuring the voltage at the point where the electricity enters your house.

[Slender]

Drift between L and protective earth (PEN)

how to measure that?

[Slender]

It is impossible to have 0V with shared neutrals on an old TN-C installation, if those 0.5V would case problems, then literally 30% of all people in Europe would have those problems and it would be impossible to use computers in any building older than 1985.

I had 5+V drift during the day, and even up to 8-9V right after I turned off induction hob and ironing and oven, and now it still about 1-2V during the day but I don't have any problems.

I didn't say it's a problem, but that it's a symptom. If there's voltage between ground and neutral, it's probably coming from the appliances in your home. If that's not the case, it could be a sign of a bigger problem.

Try turning off all the power in your home and measuring the voltage at the point where the electricity enters your house.

You can have even 10 volts between two wires in the same circuit; it doesn't matter because you can use either one. The problem can exist either before or after the panel. Installing a dedicated line is usually the first step in such a case, but it doesn't necessarily solve the problem. It certainly has an effect, and it's the first thing I asked my dad to do 10 years ago.