RE: Changing draw length effect tuning?
The best answer is going to be to change the draw length to what is right for you and test to see if anything has changed. I suggest bareshaft or walkback tuning, and broadhead tuning too if you hunt with it.
Any time you change anything in you setup you have to recheck tune, and you'll probably end up making an adjustment. It doesn't have to be a big deal to fix, sometimes it just takes a few minutes.
Recheck even if you change something as small as a 1/32 change in nock or rest position, if anything became loose and needs tobe tightened, or if you moved the limb bolts at all.
The faster, more powerful, and shorter the bow, the more sensitive they will be to changes.