From memory, the theatrical version is just the characters going from escape room to room and the last 10 to 15 minutes are completely different.
There’s also a different prologue that links to the different ending - plus the return of Deborah Ann Woll in a plotline that makes almost zero sense!
I saw the “Extended Cut” first and much preferred that, I have to say.
Also, why do I feel like both have different outcomes (as in, how the hell would a Part 3 be made without confusing the audience!?)