what will be the effect on moving the variable resistor on voltage? will it give me higher Hashrate/ or put me into the power cap soon? and will the asic be damaged if all left or all right? or it is safe to play with it?
You can definitely increase voltage if you have the cooling (which it seems, you do). Especially if you decide to go for watercooling, you should have enough thermal headroom to give it more power through that potentiometer.
Reducing it from stock may be interesting for improving efficiency, but as far as I know these are already individually tuned by the factory and set to a good safe value. So if anything, I'd find it interesting to see how far it can go with ample cooling and higher 'power target'.