The level window is a window, not a minimum — an NPC will turn you away if you are under it or over it. You choose the hunt size when you accept, and the bigger sizes pay more for every kill, not only more in total. The three sizes pay 10%, 12% and 15% of the experience the monsters themselves give you, so the longest hunt hands back about a seventh of the experience it took to finish. That is why taking a bigger hunt is worth it if you were going to kill those monsters anyway. Rewards are not capped, so one hand-in can carry you through more than one level, and there is no daily limit and no limit per visit. One NPC will not buy your drops while it is already paying you to hunt the same monster, so finish the hunt first. The Jotun Tribesman asks for fewer Lava Golems than his level would suggest. Lava Golems are much tougher than anything else you are sent after at that level, so the hunt is shorter to keep it a fair length. He pays the same share as everyone else.