Personally I think all of the trolls "get bigger" when they become adults much more than humans do, and that they're physically a lot stronger than they appear as kids. I think the comic already showcased this a lot with Kanaya being able to lift that ginormous chainsaw with ease, and Nepeta hunting things for sport. I think they, like humans, will have a second growth spurt and just get "bigger" physically lol.

In the Friendsim they describe the adult trolls as way larger than the kids, and one of the kids is literally super huge so how big is the adult troll she was talking with yk? I also think this is why Karkat just got buffer as an adult, not just because of the whole war thing but you can tell that him and Kanaya physically got way taller or bigger than the humans around them. Bro just had a growthspurt and all that war really does wonders for working out I guess.

I always imagined they're similar to ants then any other bug, and ants are also a lot stronger than they appear to be.