Does the power supply affect the computers performance. Is it worth it to go for 80+ gold?
No, a power supply doesn't really affect the computers performance but higher efficiency ratings relates to better efficiency, power draw and better quality components. If you have a bit more to spend, it is recommended to invest in a 80+ Gold power supply for the reliability.
It doesn't matter, it's just the efficiency of the supply in question. No, it's not worth it, instead, focus on the wattage.