Overall, broadhead weight and size depend on your bow poundage, your bows IBO speed, and the type of game you are hunting. I generally use a thunderhead 125 with my 60# bow because it increases my penetration. But that is for my bow, your bow may be different. Of course size matters if you are going hunting for Elk or for Antelope. You wouldn't use a 85 gr. broadhead on a bull moose nor would you use a 145 gr. on small varmints. I hope I helped ya some.

Bow draw weight:
45-55 = 100 gr.
55-75 = 100-125 gr.
traditional bow: 145+

Taylor