I'm an 11.5 in all my running shoes and sneakers and I was an 11.5 in this boot as well. The flex rating is going to be like a guide but the fit is going to be a little more versatile fit because of that lace to toe feature.
I was able to get my hands on a pair of the new Briksdal MTN GTX from Crispi February of 2022 for product testing. First initial impressions on the boots just from the ergonomics were they look fantastic, feel very light, and very quality built. When I tried them on they immediately felt great...