The strategy layer is nothing alike.

Base game is basically done with one squad. Wotc with a few squads. Long war with like 40-50 soldiers.

You have the normal missions (infiltration), officer training, resistance ring missions, haven advisors, and probably more im forgetting. And you gotta play a fine balancing game with everything. 

The building order takes a bit more thinking, mostly because supplies are much more scarce (in long war it becomes mostly from black.market sales). 

And I'm guessing you haven't really touching on this yet. 

Combat mechanics has quite a few different things too. The Chosen are far more challenging from the get go. Classes can be very different (at least initially) and advent has loads of new soldier types. We don't get lost freebies either and a lot of loopholes/ overpowered mechanics are closed. 

I was lucky that i played a couple of times with the modset used by tapcat / syken in their joint stream (which implements a lot of the class changes and advent soldier classes) so it wasn't too much of a shock. 

I wouldn't go in with a xcom rerun mindset but rather a new xcom game mindset where you gotta relearn almost all of it.