No apologies are necessary.  We were all AR newbies at some point and are all STILL newbies at something.  

First, welcome to the board.

Why do you want a detachable carry handle?  I'm just curious.  People buy the flat top uppers because they know at some point they want to mount a scope or some type of optic.  When you do that you'll want to get a BUIS (Back Up Iron Sight).  These come in two flavors - fixed and flip-up.  The fixed BUIS is great when using a dot optic, like the Aimpoint (my favorite).  The flip-up BUIS is required for most traditional (magnified) scopes.

Therefore, if you think someday you'll want a scope, why not buy a flip-up BUIS (like the ARMS 40 or 40L) now?  If you think you'll want a dot optic, get a good fixed BUIS (like the AWESOME LaRue).

You will save money (and having to re-zero everything) in the long run.  Plus you'll get to really know your BUIS now!

I don't remember the various RRA uppers.  I just stick with the standard flat tops.  Some of those uppers have a riser (either removable or permanent - not a good thing IMHO).  Again, I think you're not getting the most versitile thing with anything other than a standard flat top.  Some folks call the standard flat top an A3.  Some call them an A4.  Some call them an A4 if it has the rail slots numbers.  

If you buy a complete upper, just make sure it has the charging handle and bolt carrier & bolt.  That's all you need for your upper.

Free-float tubes will help accuracy.  Will it help a lot?  Depends.  If you hang a bunch of crap (like I sometimes do - vertical grip, flashlight, bipod, etc.) on your rifle, you can change the POI, sometimes enough to really screw up your groups, if you're target shooting for groups.  If you want a blaster to defend your home against zombies, a free-float tube won't make much of a difference.

Same with the stainless barrels.  A stainless barrel will typically be more accurate.  The trade off might be heavier weight and a little more cleaning required.  For your standard blaster, a chrome-lined barrel is just fine.

The most important question is what do you want to primarily do with your rifle?  We can help steer you in the right direction if we know that.

Again, welcome!

Why thank you.  

Get something for the "cool factor" is always gonna happen.  That's cool.  

I'm a huge Aimpoint fan.  Eagle Firearms has the best price I've found on Aimpoints.  So low, they don't want it mentioned on here.  In fact, you see their normal price on the site, but click on one to add it to your basket and you'll see the REAL price.

I like the ARMS 22M68 and LaRue Aimpoint mounts.  If you go with the LaRue, get it from C4iGrant at G&R Tactical.  He also carries the Aimpoints, so you might want to check his pricing.  Honestly, I'm torn between these two vendors.  Nothing but the best prices and service.

You should still be able to get into an Aimpoint for around $415-$460, depending on mount.

With a flip-up BUIS like the ARMS 40 (or 40L, which is a lower profile version of the 40), you won't need a weaver gas block.  Use the rear flip-up sight with the standard front sight base.  The Aimpoint (and similar optics) are designed to co-witness with the iron sights.  In fact, I've switched over to fixed BUIS on my Aimpoint guns.  I don't want to flip a lever to get my irons in action.  

If you want a railed forend you must be planning on attaching something to it.  So, why would you NOT want a free-float system?  They don't cost much more.  Most railed forends allow better cooling of the barrel and a little more protection of the barrel than standard handguards.  Plus, you won't change POI (Point of Impact) with things attached to it (even a sling) like you can with standard handguards.  Get a good railed handguard, like the LaRue (my favorite) or a Daniel Defense (my second favorite) and it will free-float the barrel for ya.

Keep the questions coming.