These are the rules here in Canada, not sure if they apply but they are American Club shows so they should be similar...Typically the need for neck reining at a young age depends on what kind of bit you are using, at 3 or 4 years old you can still ride with two hands if you are riding in a snaffle. If you decide to move your horse up to a shank, you need to be neck reining.
A horse that is 5 and up also should be in a snaffle, I believe that 4 yrs is the last year they allow a snaffle...although you would need to check on that.
You don't need a brow band for western and any kind of western headstall is fine, but you would for english (where you also always ride with two hands). National Bridle Shop carries the ones that are fot TWH...thiken band.
Hope this helps some...but6 I would check the rule books to be sure as it could be different for you.