People who are loud and talk a lot usually have nothing of substance to say. This contrasts with "Still waters run deep." Other versions are "Shallow brooks babble loudest" and "Shallow brooks are noisy."
If you are caught between a rock and a hard place, you are in a position where you have to choose between unpleasant alternatives, and your choice might cause you problems; you will not be able to satisfy everyone.
'The grass may be greener on the other side but it's just as hard to mow' is an expression used to mean a person's desire to have that which another person has in the belief it will make their life easieris false as all situations come with their own set of problems.