Should the coolant reserve be pretty much full? I know my level is always pretty low, but I don't know if that has something to do with how the car runs. Actually, I don't know much about it at all....

Um it should be inbetween the low / full lines when cold I believe.

does the level of the coolant have any effect on how the car runs....for example, if the level is too low it doesn't run as well?

that's just the overflow tank. as long as there's coolant in there and you're not losing it 24/7 (constant refilling) you're ok.

if there's coolant in the overflow tank then it doesn't affect how the car runs.

Ok, cuz my dad was curious because right now it is just at, if not under the the min. line.