A beta would work best for his storyline for being untalented.
And also I think if the rest of the group (excluding big eyes which I would think would also be beta) were omegas it'd give them another layer to being outcasts cause they're aggressive, don't take no shit, and don't look like regular omegas (too muscular)
Like alphas are always trying to assert their dominance over them because they're omegas and most people in the military are alphas.
Also their previous squad leaders would also be alphas trying to assert dominance over them with their phermones and shit but they kept getting their ass whopped until the previous commander got the message and sent Enkrid a beta.
Honestly, the others secondary genders don't matter as much. But has to be Rem is an omega, like it's so cute he gets cold easily, and is low key possessive over Enkrid. Also in his tribe it's probably normal for omegas to he strong too
Itd also be a funny dynamic where everyone's glaring at each other through angry phermones, or they scent Enkrid all over and Enkrid doesn't notice because he can't smell phermones.