Change load_geometry to default True

[gonzalocasas]

          I like the fact that `load_geometry` defaults to True. Let's change it also in the other classes that already have functions like that

Originally posted by @gonzalocasas in #406 (comment)

This might simplify some simple examples and use cases, however, we need to make sure we don't accidentally trigger a lot more testing code to be ran because several tests seem to be relying on the fact that this defaults to False.