Q: What happens when Jump gives a jump distance greater than walking speed?
Crawford: Your jump is limited by how far you can move; each foot jumped uses a foot of movement (PH, 182).
Q: So casting Jump on a character with a 20 STR and a move of 30’ is effectively pointless?
Crawford: 20 Strength running long jump: up to 20 ft. With jump spell: up to 60 ft. with a speed of 30 ft. and Dash.
Q: A dwarf 18 STR, walk 25ft, under a jump spell, max long jump 74 ft. BUT: with dash can only go 50ft. How to get max benefit?
Crawford: The jump spell lets you leap farther than normal. Use a spell like longstrider or haste for greater speed.
Q: Monsters like Barlgura has a trait allows 40ft jump while having base move of 30. Does it need to dash to get the full benefit?
Mearls: I'd say no, but Crawford disagrees