It has significant impact on leveling time.
The "grind" coded into profiles are just for grinding the specific mobs for specific quests.
"Kill between hotspots" kills ANYTHING within a 30 yard radius of your toon on the path to next hotspot.
Personally, i leave it off for 1-93 and turn it on after. The death ratio tend to rise where the added mob xp outweighs having to corpse run.