I don’t think there is a good or better breed of dog or cat suitable or not. It is all preference.
I have seen all types living in a bus. It largely depends on what you will be doing.
Some dogs (even within the same breed) need more exercise than others.
I traveled with a Bernese Mountain Dog. She was pretty mellow - but still had challenges.
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You may want to consider what you will be doing - taking the dog with you everywhere? Leaving the dog in the bus for extended amounts of time? Some dogs like being left alone - some will have separation issues...
Cats

can have similar challenges - I guess. I have never traveled with a cat.
But I have seen several bus dwelling cats - and they all seem happy (as Josh said - Happy ignoring everyone!!

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