All the dnd/ bg3 mechanics aside, who jumps farther?
Dextrous or strong person?

LAe'Zel at least can jump farther than my rogue. What interests me is if the movement consumption is based on the action itself, so that a jump always deducts 30% or so, or if it does so proportionally to the jumping range. In the former case, always doing a jump could make you move further in every turn when giving up your bonus action.

Not just Lae'zel, any Fighter can jump the same distance as her.

I beleive it is complete Strength basis to jump, Dexterity might be related to movement speed though .

In D&D your Strength determines how far you can jump. Not sure if Athletics (Strength) plays a part. Maybe Dexterity or Acrobatics (Dexterity) plays a part in falling. Really wish LARIAN would SCRAP their horrid UI and give us one decent character sheet with ALL pertinent information. What we have now is beyond bad.

Sadly there is indeed no way to determine the height of a ledge, so no guarantee if you take damage from a fall or not regardless if you hav that thief trait. I do suspect that no ledge is higher than 8m, though, so I really do not see why the thief trait should not apply here.

If the OP is talking real life, that's not an easy determination. Real life people don't have neat and tidy stats to mark dexterity and strength. That said, I'd say jumping far is more about strength than dexterity. Dexterity is more a marker of how coordinated you are with small tasks...things you do with your hand. agility is the more general term for a lot of the stuff we place under Dexterity in D&D which is part of the crux.

See, in D&D if the Strength stat applies to pretty much all types of strength and muscle development. In real life, a person might the equivalent of 14 Strength in one or two applications but not most of the others. And also note that 14 Strength is going to generally be the strongest person most people know. 15s+ tend to be uncommon and 18s are extremely rare. In any stat. Again correspondence to real world capabilities is fuzzy at best.

But yeah, Strength for distance, Agility for accuracy.

In real life, strength is about how far and dexterity is about how safely you land. And it really depends if you jump from standing still or you can run before jump.

Amusingly, my Dwarf - with 16 STR - can jump as far as she can run

Unfortunately DnD only seems to take strength into account and not the mass of the creature jumping, under these rules an elephant would be one of the best jumpers around leaping vast distances

I'd prefer if it were based on either the character's Athletics or Acrobatics, whichever is higher.

and now I'm remembering jumping over cities in Morrowind. Good times.