The wingspan method will get you close , and close is not good enough , its a starting point . Go to a good pro shop and get it dialed in dead on , many still to this day shoot too long a draw length , a 1/4 inch will make a big diferance .

As far as straight arm ,vs bent arm , you will get many varing oppinions on that , even amoungst the pros , shoot what feels best to you , I am more consistant with a slightly bent arm , for taget and hunting