Generally 4 hours is not too long of a car ride for bunnies. I’ve taken my bunny twice back to my parents’ place and it’s around 4 hours away. He did just fine

That being said, it also depends on the tolerance of each bunny. You can drive him around the neighbourhood for about 5-10 minutes and see how he reacts to car rides. Some bunnies get really scared while others are quite relaxed. You can put something like a toy or a blanket (anything that he is used to having in his area at home) so he doesn’t feel like everything is foreign.

For carriers, it should be small enough for the bunny to not get flung around if the car needs to brake in an emergency, but big enough that he can stretch out fully. I find that sturdy plastic is better than fabric in terms of material as some bunnies will pee in a car – plastic does not absorb and is easier to clean. I put a pee pad in the carrier and some hay for padding/food. Some carriers are top opening while others are side. The side ones are easier to “lure” the bunny in, but it can be difficult to carry them out of it if they refuse to come out. There are pros and cons of both so it really depends on what’s available and better for your bunny.