How a larger Bismarck would escape the Baltic

Would a larger Bismarck-class battleship be trapped in the Baltic if it could not use the Kiel Canal?

Not necessarily, but it would have to use the Danish exits or Germany would need to widen the Kiel Canal.

A larger Bismarck would turn a design increase into an infrastructure problem. The ship could leave the Baltic through the Danish routes, or Germany could enlarge the Kiel Canal. The first option exposes movement to geography and enemy observation, while the second demands a major construction programme. Such an expensive prestige project would not have been out of character for Hitler's regime.