You're good. It's just starting to get there - welcome aboard, by the way.
Sometimes it's tough, without information. I'm sure you don't understand the level of information required to diagnose a gun issue over the internet - but we're well versed in that. No harm, no foul.
Carrier weight on those two is gonna be right around 18oz, not enough to differ between the two. Fulton Armory parts are top-notch, nothing to worry about. Best quality out there.
AR15 rifle extensions, A1, A2, doesn't matter. .308 AR rifle extensions, same. 9 11/16" internal depth. Your buffer should be 5.200" total length, weigh 5.4oz.
Recoil spring. Only ones I'd run with that combo would either be the Armalite EA-1095 spring, or the Sprinco Red spring. Don't trust anything else - it hasn't been confirmed, repeated, or mass produced with perfect results.