In my experience, water-based polyurthane produces the most bubbles. It's best not to use a roller when applying water-based poly.
I use oil-based poly on all my wood work. Also, I'm not liberal in my application. In fact, I am careful to put on multiple thin coats of poly. And, when I sand, I use the Very Fine sand paper. Some folks even use a fine steel wool. (I don't.) You don't need to press when sanding because all you're trying to do is 'knock down any high spots'. Really, it's a very light sanding. I use a foam applicator; not a brush. To be honest, a foam applicator is all I've ever used. In doing all I've described, I've had excellent results. I've done baseboards, fireplace mantles, doors, stair banisters, handrails, etc., etc..
Good luck. And I'll be curious what others have to say on this one. I'm always looking for ways to get even better results in my work.