I have 3 dogs. 2 beagles and a rat terrier/beagle mix. They all ride in the back. I fold the seats down, use D-rings to anchor them, and leash them up. They enjoy it for the most part. They get a bit anxious going on rides though. We did a road trip to Colorado and they chilled in the back the whole time.
Sorry I didn't read all the posts but I wanted to add my personal input. I truly believe that owning a dog is privilege. I have found that my dogs are extensions of my or my wifes personalities. You need to find a dog that you are interested in and that you'll bond with, and then it all comes down to training that dog and your relationship with them. All breeds have different attributes they excel in, so you need to ask yourself what you really want. An active, lazy, obedient, independent, dependent, etc. Definitely please do research on specific breeds and find what sounds like a breed you'd be into. Consider house or apartment size, food budget, kids vs no kids, other pets in the house, etc. My vote of course is for beagles. So things I know.
1. any type of herding dog is extremely intelligent, high energy, and great with obedience training.
2. Shepards, boxers, pits, and Dobermans are very protective, loyal, and dependable.
3. beagles are very independent and curious, and depending on their diet very energetic or lazy.
4. weimaraners and vizslas are awesome dogs for being active. I prefer vizslas over weirmaraners.
Good luck on your dog search and enjoy your new best friend.