If I use straps, how much will my grip strength development be affected. How do I develop my grip to make up for the straps? At what point should I start using straps. (Ex 20 unassisted chins)
Yes it will hinder your grip by assiting it.
I suggest not using straps or only use them AFTER your grip has failed you. Try and go with out it as MUCH as possible.
If your grip is failing on chin-ups, then you have big ass problems. Unless you are doing 500 in a row.
You have an obvious weak spot here. You can either ignore it by using straps all the time, or you can do some specific training to address your weakness.
Phill is wise - listen to the Phill......
Go to the Grip Board or Grippermania. They have some of the top names in the grip world posting there.
If your grip is failing on 20 chins this is more accurately an endurance problem rather than a strength problem. Build up your grip endurance by doing timed hangs on a bar. E.g. 30 seconds in bottom position, or 30 seconds in top position of the chin up. Then build up the time.
Unless you are really heavy I can't see grip being a problem, for instance if you were deadlifting only bodyweight it would be a similar grip strength?