Everything is downsized when you move from an A to a B. The bathroom is smaller, usually a wet bath (meaning the whole room gets wet) and the tanks are smaller. When you are in a campground with full hookups, of course, you are only limited by the capacity of the water heater and some B's have tankless on-demand hot water. Others have smaller tanks (ours is 6 gallon), but the water gets plenty hot so you get much more than that when it's mixed with the cold.
When you are off-grid and using the water tanks only, there is a button on the sprayer so you don't have to worry about the temperature mix when you turn the water on and off - but you can't stand in a full shower for very long.
Our B has a two-burner propane stove - your A probably has three or four burners. But even at home we never use more than two at a time, so it hasn't been an issue. We also carry a propane grill and cook outside if weather permits.
Some B's have an induction cooktop instead of propane burners. Most B's have a microwave and some come with a convection/microwave combo. You will need shore power, a generator, or significant battery power and an inverter to use them - which I suspect is just like your Class A.
You will have a LOT less counter space.
You will have a LOT less storage space.
To be honest, I think most of these are not really significant compared to the reduction in stress from having to maneuver a Class A.
However, the biggest change may be in your interactions with your traveling partner. There is no "me" space in a Class B so you need to be able to be together amiably. There's a lot of schooching out of the way so the other person can pass and since you don't really have a private bedroom, owls and larks have to learn to get along - and maybe wear earplugs.
But you can probably park your B at home and shoot out for a couple of days whenever you feel like it. And you can go pretty much wherever a truck can go and park in a regular parking lot. Having a Class B just makes things so easy, I wouldn't trade it for any other camping experience.