I currently have a 1 atk, 60 str pure, and was wondering is it worth getting high str on this obby mauler? or should I get 40 atk, high str, 1 def and pk in F2P?
If you like F2P pking, get 40 attack and high strength. If you aren't sure / don't like F2P PKing, stay 1 attack and get high strength and PK with an obby maul.
Considering your current stats the best possible option for you would be to become an obby mauler pure. If you were to become a f2p pure you would have to train attack up to 40 which would be a waste of time in my opinion because F2p pking is not worth the time. It has little excitement, action, or rewards. You would be much better off with an obby maul as long as you keep training strength up and get 55 slayer for slayer staff.