This is one of those questions that everyone has an opinion on, just like the which caliber is best drunken camp fire argument. However I do not believe this has the same amount of wiggle room. And obviously this is my opinion. You need to work with your archery shop, to use their chrono to come up with a rig that works best for your draw length and weight. Never use a mechanical broadhead, and I would say a 100g broadhead is the bare minimum. 125g is better. Use the online calculators to figure out foot pounds of energy with your rig. On this I would say 65 foot pounds in the minimum and 75+ is better. All of this comes down to your overall arrow weight, not just the broadhead. A quality arrow, potentially a weighted insert for more forward weight, and a 125g broadhead will do the trick. I am shooting a 525g arrow, 68lbs draw for elk this year.
The stick and string is a primitive weapon. This means to properly respect the animal you need to practice way more and do the research to make sure your equipment is as lethal as possible.