Over the last 6 months I've bought a Norc Z lower, LPK, slab side upper, , muzzle brake, 10.5 barrel, and 2nd gen 9 inch rail from SFRC. The only issue I ran into was that the rail was VERY tight to the receiver when turning it into full lock on the barrel nut. Everything else I got from the spare parts box I've amassed.
Other than that no issues mechanically. Looks and color and such are personal preference.
I'd shy away from the bolt carrier groups. They have a bad rep and I don't need to be the one to see if they still deserve it.