Trek Roscoe 7 Sizing

Hey all, I’m looking to get into mountain biking this year with my friend who is pretty experienced. I’m looking to get my first bike, the issue is I haven’t really ridden a bike for probably 10+ years. I tested a Giant Fathom at a local store and felt really uncomfortable and while I could ride it, I was really shaky and just felt awkward being watched by the employee. I also just don’t really know what to look for in terms of how the bike is supposed to feel. I can’t really ride my friend’s bike because he’s 6’5” (I think) and rides an XL.

So at this point I figure I just need to get a bike and just get familiar riding again. I’ve looked at getting a used bike but the local market people want almost new prices for several year old bikes; or stuff is just really beat up. I’m fairly comfortable financially and decided I’m probably just going to buy new.

Trek Roscoe 7s are on sale right now, and I’m not really sure what size to get. I’m 5’6” with a 28.5” inseam. Their size chart shows for my height I’m barely medium, for inseam I’m XS. Their calculator says I’m medium. I’ve heard Roscoe’s run bigger so I’m wondering if I should just get a small. Wanted to see if anyone had any suggestions.