We always back into the garage because the line of sight is shorter over the hood when leaving than out the back window (especially with the pickup truck) and one is more likely to walk in front when getting in. That gives an extra look to the exit path. Neighbors frequently have very little ones around, which they do watch carefully, but I want to be careful around them too.
The Honda backup camera has lines denoting "distance to go before crunch" and that works fine. For the pickup, I picked a wall stud to line up the driver's side window frame with. It's worked for 17 years so far.
As far as the exhaust goes, yeah, don't inhale.