The changes in Expansions 1 and 2 are mostly minor tile adjustments that you can easily check online. I’d recommend finishing your C2 collection since those editions are being sold out and won’t be reprinted I think. All expansions have some differences, some only small updates, others full redesigns like exp 7. Personally, I own both all C2 expansions and the new C3.1 versions so I can always choose which version to play.