1. Yes, feathers are faster because they are lighter, but only out to about 60 yards, then the vanes take over because of less wind drag.
2. Feathers may be more accurate for broadheads because they disrupt more air causing better stability.
3. The only thing straight vs. helical is spin. The more helical, the more spin.
4. Feathers are lighter, so it depends on your total arrow weight weather it will be an issue or not.
5. Color makes no difference as it relates to speed.
6. Wraps do add weight back to your arrow, but I think it is about 12 gr.

The big disadvantage of feathers is that they don't like to be wet, so waterproof them.

Hope this helps! Good luck this year.