I've got an S&W VTAC2, which claims to have a chrome lined bolt carrier and gas key...however, I'm confused. I'll admit I'm very new to AR15s, but won't chrome lined look shiny? If yes, then why does the bolt look like this?
Chrome lined means that the carrier is lined inside with chrome. So if you disassemble the bolt carrier group then you'll see the inside of the carrier where the bolt goes is lined with chrome, and often times the gas key is lined with chrome as well. It does make cleaning a lot nicer, no doubt about it.
As far as a full auto carrier, it's main advantage to you is that it is heavier than a semi carrier because it's constructed a little differently. So no reason you necessarily need to switch carriers, especially if you're just plinking away with your gun for fun. The main advantage if the heavier bolt and buffers is that they slow the bolt down which means a little less recoil and faster follow up shots, unless you're running suppressed in which the additional weight is much more advantageous. So I wouldn't necessarily advocate you switch to an auto carrier, no need for that really. By you might find a heavier buffer would change the recoil and allow those faster follow up shots, which depending on what you're doing might be something of interest to you.