No way could a large linebacker type guy compete in international gymnastics.
It’s not a question of the equipment being strong enough, it’s that he couldn’t move his body around quickly enough, and wouldn’t have the strength to get himself into the various poses.
To illustrate, imagine if this were, say, a pullup competition: the guys who does the most pullups wins. Do you want to bet on Lawrence Taylor or on Paul Hamm? You’d take Hamm every time because he has less wait to pull up.
Similarly when it comes to doing flips on floor exercise, to be successful you need the right combination of (1) high strength and (2) low weight. Based on past olympic champions, it looks like the ideal for men is somewhere between 5’ 5" and 5’ 8" (Mitch Gaylord is 5’ 8" and he’s on the tall end) and somewhere between 150 and 170 pounds.
Regarding the timbre of the voices, remember that the women are usually under 18 years old and they also tend to be very small. Their larynx’s are smaller just like the rest of their bodies. Regarding the men, I think I have noticed that their voices tend to be a little bit on the high range. I guess that is probably due to their being smaller than average height, but then again I don’t normally think of men between 5’ 5" and 5’ 8" as having particularly high voices.