I just bought this game with 2 expansions for a new family game. A few questions, please..

Is it best to keep to the original for a while before introducing the expansions?

When you mix expansions, does it 'break' the original scenarios?

When storing them in compartments, do you mix all the components into one or two large Plano boxes, or do you keep the expansion components separate?

Thanks in advance!

The expansions mostly just add new cards to the decks and new monsters and effects and such that you can check the rules on when they happen to come up, so there's some increased complexity, but not a whole lot. The particularly noteworthy things are treachery (all expansions) and feats (ToI), which have their own special rules and each give a significant power boost to one side.

I store all my components mixed together.

We sort the components out into ziplock baggies to make finding them when building maps easier.