Elves in “The Dragon Prince” are bird-boned
Let me explain:
Humans are capable of fighting elves equally, sword to sword, despite the greater lifespan of the elves giving the elf warriors a significant training and experience advantage. Since one human can fight three elf warriors at the same time and win, even when the elves are also using magic, it doesn't seem that elves are physically stronger than humans.
Yet, elves can leap into trees like monkeys or cats, and race across the branches like squirrels. (EDIT: Callum couldn’t walk across the stepping stones without them sinking, but they didn’t move at all when Raylla stood on them.) If the elves are not super-strong, then perhaps they are super-lightweight. Perhaps bird-boned.
If they are bird-boned, that limits how strong their muscles can be, because their bones can only withstand so much strain. Their muscles could still be strong enough to propel their lightweight bodies up into and across trees, while still being weak enough that humans have a brute-strength advantage in hand-to-hand combat. An advantage that elf warriors need their greater experience to counter.
Weaker bones would also limit elven endurance. They can leap into and across trees by exerting a lot of their strength, but perhaps after a point their bones start complaining from all of the strain. Certainly, it would mean that elves take more damage from getting hit than a human would.
Finally, this means that even noodly Callum might be able to princess-carry Rayla without difficulty, which is arguably the most important thing.