I personally go 3x for gym classes like "healthy spine", "mobility", "core" etc. and then 2-3x hard training. But I would say I am very active recently.

Do I feel better? Yes. Was it hard first 2 weeks? Yes, I had even to resort to painkillers.

I think the best for people who sit a lot are core, mobility and back exercises. Huge motivation for me when I finally started prioritizing back on machines and progressed on all other things and finally look like I go to gym :)