BB grow better in a wet environment, trickle filter or bio wheel, however they grow on every surface as long as there is oxygen in the water and a source of food (ammonia/nitrite). Having more surface area for BB to grow is good, having more than is required to maintain water quality is just an expense, if you have more bacteria then there is food, they will die off until there is an equilibrium. Same if you increase the bio load of the tank, the number of bacteria will increase.
Hope this helps.