Just to echo what the other posters have stated... It doesn't really matter what gate you end up at, some are more of a walk than others, but customs and immigration is very fast and easy.
You don't need to check in during your flight for the next one you can check in at the counter the next day since you'll end up needing DOC check anyway (lines are never long IME anyways).
I recommend the exit row for preferred seats (22A, B, H, J) Those are probable the best non C+ seats in the main cabin. Keep in mind that E fares are now systemwide so even though the seat map may show very open for a flight you might have 50-60 people clear into seats on day of departure.