In short, some people think it doesn't matter as long as you know where to holdover, others thinks going out to 30 or 50 yards (instead of 15 or 20) gives you more accuracy.
My view is that it doesn't matter as long as you test it at a range of distances when you are done. I find it easier to zero at 20 yards because there is less random variation in the poi. I zero at 20 and test at 50.
The trajectory is based on the speed. 177 is only flatter when there is a power restriction like at matches.
There probably won't be much difference in trajectory between a 22 and 177 both traveling at 900fps except that the heavier pellet might travel further.