I have fat feet and fit the gtx trailcross fit nicely. I went a size up as I do for all adidas shoes. I only wear them with normal socks but it’s not like you need thicker or waterproof socks with them IME as they do a good job of keeping your feet dry and warm.
I’ve not noticed any difference in grip either, unlike the freeriders I bought with the recovered ocean plastic, they’re really not up to usual 5:10 standard.
I have some EPS low in Brighton and based on my first year with them, it’s rarely cold enough for them in the woods down here. I’d say 8C is the absolute max temperature I’d wear them in. I’ve got some Freerider Pro Mid which I’m more hopeful of but I’m still using my Freerider ELC for wet/muddy conditions.