This sounds about as legit at the people who say 'face follows face' when in reality land a ten value card follows a ten value card roughly 30.8% of the time in a neutral count. In all likelihood you are seeing patterns where they don't exist. > Whenever I get 20 the dealer always seems to get 21 Most casinos won't bother cheating because they have a built in edge and most players play very poorly. If the cards are being changed out of view of the players you cannot be certain the decks have all the correct suit/ranks. If they are using automatic shufflers you have no way to know for certain that they are shuffling the cards randomly.
You could even be cheated in a brick-and-mortar casino. If you have any doubts then you should not play. The problem is you have no way to know if you are being cheated.
Some sketchier ones might well be rigged.