The N-SSA is a completely different world than the reenacting world. N-SSA puts practical shooting above historical accuracy. For example, you see people on the firing line at N-SSA events that would be laughed off the field at reenactments (modern eyeglasses, visible wristwatches, fantasy uniforms). It all depends on your perspective. I venture to say that a truly authentic reenactor would be at a distinct disadvantage at an N-SSA shooting event.
As a collector, I frequent the "sutlers' rows" both at reenactments and at the N-SSA Nationals. Prices for guns and accoutrements are often better there than at purely collectors' shows. (This is a form of "arbitrage.") I used to do reenactments, back in the 1980's, but I think basically this was an excuse to further my collecting. I did not only Civil War, but also Rev War, WW1, WW2, etc. Still have all the gear for all those time periods.
Collecting the guns is only the tip of the iceberg. You have to have everything else, including the personal equipment, to put those guns into context.