Op said he is 5"7' 168lbs and thats roughly what i measure. I have a 29" inseam, long torso. Op didnt say his inseam
For reference, the reach on my med is 430, large is 450 and my medium commencal meta am 29 is 470. Commencal is longer than most and ive put a 32mm stem on it. 455 - 465 would be my sweet spot for reach with that 32mm stem. A large decoy with the 35mm length i have on it would be preferable. Really like my medium for most things. Its a great bike and well built. I just think the large with 450 reach would be damn close to the sweet spot. The 470 reach on my commencal demands higher speed than tight xc type trails. I do go fast sometimes on those trails because it works better but overall it can tend to struggle a bit there. Bike park speeds and steep gnarly stuff and it really comes alive with the 470 reach but it has a shorter chainstay then the decoy(only 5cm). Latge decoy with 450 reach , 180 fork, my -1 degree works headset, slack setting on the chip, and one offset bushing would have the head angle and wheel base very close to the commencal(i upped the fork on the meta to 180 as well). Decoy would just a touch shorter reach and wheelbase and that be perfect for my area, use and fit.
For you id say the debate would be xl or xxl. They both have adequite standover but i think the large would give you good standover and youd be able to get a dropper post with long enough drop. You may want to confirm the seat tube lengths to be sure. That would probably be the deciding factor in my eyes. I think one up dropper still gives the longest drop in the shortest post, but there is some new posts that may challenge that