I'm a fan of hot and fast bugers... with grease dripping down on the heat and sizzling. Mostly cause that's what I always got growing up, and to some degree it's a nostalgia thing.
However, if making burgers in mass quantities on a pellet grill, I would never try doing the traditional hot and fast... In fact, I really wouldn't recommend even trying cooking a entire grilling area of burgers above 325F on a pellet grill with full drip pan, it's very likely a recipe for a grease fire. Yes, you will get sort of a 'oven' baked product at lower temperatures... and it could actually take a while to do...
Lets say you have a pellet grill that's 20x34" cooking grate... first, I wouldn't hang the burgers over the outside edge of the drip tray, to prevent grease from dripping down underneath the drip tray... so you probably end up with a cooking area that's closer to 16x30". I would estimate you could fit probably 18 burgers on a grill that size maybe 21 if you used the full width of the grill. So, to cook a 100 burgers you need to make like 5 full grills worth of burgers. If it takes say 30 minutes per grill full , your looking at 2.5 hours of cooking burgers. I suppose you could start in the morning, and place cooked burgers in a warming pan until time to eat.
If you had a charcoal or gas grill that large, you could do it in less than half the time... ( but then not alot of us pelletheads have charcoal grills that large, or even gas... ). Problem with cooking over high heat , is the grill master needs to constantly be working.
Anyway, good luck.