Hi Reenie, the play mechanic is mostly the same for all of them; what makes them different and slightly more or less challenging are the board layouts, obstacles in your path, whether or not they are timed/untimed. Other variations include different kinds of power-ups, things that you might get to do between rounds such as accumulating enough money for buildings that generate useful things in order to conquer more difficult levels, and also the themes.
Over the years there have been some clever iterations, however, that build upon that mechanic into something quite different.
A good example is Claws and Feathers.
While the match-3 mechanic is there, the game involves heavy elements of strategy that can be quite challenging. In fact, you could call this series as much a strategy game as you could a match 3.
The above is just one example; there are many others.