I travelled with a puppy (well until he grew up...lol)
At 2 months he needed a rest stop every hour or so. It took forever to get anywhere...
cause I spent more time looking for someplace to pull over for him ro pee than I did driving I think.
I had a Class A RV at the time so I bought a babies collapsible playpen for him to travel in and wedged it between the two club chairs in the living area. The last thing I needed was a small puppy playing with my shoelaces (his first new 'trick') while driving down the interstate! It's a good idea to restrain him no matter what you're travelling in, you don't need the distraction of a puppy climbing on you while you're doing 60 (or 80!).
I don't recommend puppy pads, puppy needs to learn to go outside not in your home. Be prepared to get out several times a night for him to go pee. Because we ended up at truck stops and rest areas a lot of the time, I think I just slept in track pants and a sweatshirt for his first couple of months - a pair of slip on shoes and I was good to go!
And yes, the better the brand of puppy food, the less poop and the healthier the puppy.
Start leash training him right away of course and then when you're away from traffic, he can be started on basic commands. One of the most important training, IMO, is not to exit the vehicle until you say so. This will stop any chances of him running out in to traffic at rest stops and truck stops.
If you're interested, there's a wonderful forum specifically for dog owners - dogforum.net I found a lot of help there while dealing with my last 2 dogs. And of course, here, where we understand travelling with dogs more than anywhere else.