@Woubeir
To the original question about stiffness of a boot but foot climate of a trailrunner, check out approach shoes, which are made by multiple manufacturers for example those from FiveTen http://www.fiveten.com/us/.  The FiveTens I have used are very stiff and the soles are very grippy. The footboxes often run a bit small so you might need to size up.
FiveTen also make mountain bike shoes with SPD “clipless” mechanisms to clip your shoe to the pedal. The FiveTen website describes their MTB as having supportive carbon infused midsoles but I have no experience with them and cannot judge the claim.