WRT Schwinn, don't remind me- I had a Schwinn Varsity after my Sting Ray bikes were stolen and I bought it with "If they want this one, they're gonna have to work to get away and suffer". I think the shorter cranks are for ground clearance, AFAIK, but the same can be achieved by raising the bottom bracket- since the geometry of a road bike and MTB are different, the change would be less noticeable. I never knew the crank arms that I had installed on my road bike are different until someone saw the ad I placed on FB to sell them.IMO, 5mm doesn't matter between R&L sides because riding a bike has so many moving parts, including the rider.
My idea of comfort at this point is not taking a digger caused by jumping over things. I did plenty of that when I was a kid- I'd like to survive the ride. A friend had a yard sale on a trail a few years ago and ended up with a broken collarbone and jammed shoulder- he has always ridden a lot, but it can happen to anyone.