1st of all if your going to d one you have to do them all otherwise your arrow wont fly straight
Not what I and others have noticed - they fly the same with cock feather straight.
If you are going to shoot fixed heads I would not recommend a straight fletch. I few degrees 2 or 3 will make a big dif IMO and be a much more forgiving setup.
Also feathers are MUCH more forgiving when it comes to rest contact. You can shhot them real well even if they are touching the rest a bit.