This type of post comes down to how you intend to use the rifle.
Since you have selected the entry/tactical I will assume that high power marches,service rifle matches,and serious varmit detail is out of the question. Therefore I suggest the full chrome lined barrel. I myself have used an AR for about every possible use and with almost every possible sight system and have yet to be bothered by the fixed front sight so I wouldn't bother spending the money on the YHM.I have an Eotech and have used aimpoints but have onlt slight experience with an ACOG. They are supposed to be fine but the several times I have considered one I just spent the money on a complete other AR. You could almost buy two complete uppers for the price of one ACOG.If you are going to be shooting on a two way range (LE/military) they might be something to consider but I don't see the use for the average guy.
Yes,get the removable rear sight,either the one pictured on the RR or the normal carry handle type.
I would suggest you purchase the Rock River National Match trigger at time of purchase as it is a great all around trigger that will improve any type of shooting you intend to do.
I would also suggest that you buy a Ceiner rimfire conversion,go to Brownells or better yet find someone who gets a discount there (dealer or C&R holder). I believe the current price is about $150 with one 10 round and about $120 with the discount. Rimfire out of the AR is a total and ammo is dirt cheep.
I also find for lots of uses a scope to be useful/fun. I perfer the quick detach B Square nount (goes right on the flatop). Try to steer clear of the cheep chain store scopes,they are pretty poor compared to what is available for 100-200 bucks.I like a Leupold 1.5-7 Rifleman which I bought at midway (again with my C&R Discount) for $199 (2005). This scope is so much better than the $89 chain store stuff that it makes them look like kids toys.
You see the problem here right ? once you buy an AR ther is a never ending list of "stuff" you need for it. Sights,scopes,Uppers, do dads,add ons and so forth. All of this is refered to by some as "Black Rifle Disease" (BRD)
Lots of fun !!