It depends what you're rewarding and what the dog enjoys most. If you're actively training a new behavior, good, high value rewards are important to help the dog catch on faster and keep them interested in training. If you're just acknowledging good behaviors as they naturally happen less can be more. For instance, when a new dog comes into my home, I give them quiet praise and gentle, soothing pets when they show progress settling in, such as when they sit and watch, or lay down on their own. Since I'm rewarding calmness, I don't want to excite them with the reward, so I let them know I'm pleased in a way that doesn't undo the progress they're making. But if I'm working with a dog who barks and lunges on leash, I'll use the big guns - I'll get down at their level and use high value treats and a lot of energetic praise, since the goal is to be more interesting than whatever it is they are usually distracted by. Match your reward system to whatever the situation calls for.
But the most important thing to keep in mind is to reward with something that particular dog enjoys. Many dogs enjoy petting, but many others do not. They may tolerate it, in the way you might tolerate someone getting a little too huggy with you, or the way a child tolerates cheek pinches from elderly relatives, but you'll know the dog who is really enjoying being touched. Pay attention to what makes each dog uniquely happy, be it praise, treats, a toy, belly rubs, whatever, and use that to your advantage. If you have a dog who isn't particularly food motivated, try rewarding by tossing them a ball, or playing with a tug toy for a few seconds.