I was wondering: I am on a 1700 cals/day eating plan.

Suppose I eat 1800 calories one day. Should I then eat 1600 the next day to even it out? If so, how far does this stretch? If I eat 3400 calories one day, I obviously shouldn't refrain from eating the next day, but what about a "transfer" of, say, 500 calories?

nah dont bother with anything like that
if you eat 100cal's over, or ever 500 cal's over dont try and fix it by eating less, or doing more cardio, its best just to stick to your proper diet as best you can