The make and model of your bow will help with telling you what to do ! Yes most strings will come the correct length, BUT hardly ever will you slap on strings and cables, and everything come out right ! It's the nature of the beast, and there's too many varibles! IF YOU EVER have a shop slap a new set of strings on and then hand it right back, I suggest handing it back and tell them to re-tune the bow, cause it won't be right 99 % of the time !
Here's some stuff off my head that may help you some !
2-CAM BOW=
ADD TWIST TO STRING= shorther draw,lower weight,small BH change
UN-TWIST CABLES= shorter draw,lower weight,small BH change
ADD TWIST TO CABLES= longer draw,higher weight,small BH change
UN-TWIST STRING= longer draw,higher weight,small BH change
ADD TWIST TO STRING & CABLES (EQUAL AMOUNTS)= same draw lenght,higher weight & BH (Brace height)
UN-TWIST STRING & CABLE SAME AMOUNT= same draw weight,lower weight & BH
1-CAM BOWS
All above exactly the same expect the last 2 ! to keep draw lenght the same you must twist/un-twist the strings 2X more than you do the cables.
Hope this helps some!