I don't know the depth of hex in those Xmaxx wheels, but I'd go with the +2mm hubs. You don't lose much even if they're a tiny bit more than you need, and it is better to be safe than sorry.
I used the 0mm stock offset hubs with some Arrma Backflips (not following the advice on this forum to use +2mm) and the result was a huge mess of melted plastic. Luckily, even though all 4 wheels and all 4 carriers were slightly damaged, none of them was ruined, but we're talking about well over $100 worth of parts that were damaged due to using the wrong hub.
All that happened after just 1 run (the power of the motor I use is so insanely high that I couldn't feel the resistance of the wheels rubbing on the carriers).
If you get a chance, I'd love to know the outer diameter of those X-maxx tires. They seem pretty large, which means you might need the smallest pinion (15t) and a low kv motor. Otherwise your overall gearing will just be too high and motor temps might be a problem.