RE: What I've decided: I haven't made any new decisions yet. I need to research each component listed to determine the pros and cons of each one and weigh them against cost. That'll take a little time.
All the work has been done for you so I'll give you a couple of free fish-
Build a basic configuration carbine with a 16 inch barrel. It will do anything you ask an AR to do. There are a couple of niche areas where a more specialized configuration is better but even then, the 16" carbine will still do the job. The middy gas system isn't significantly better than a carbine gas system but the longer handguards of the middy offer an advantage.
Use a good barrel. Barrel material and chrome plating are not a big concern to the civilian shooter as long as you choose a quality barrel. If you choose a match barrel, realize that you'll need to use good quality ammo to get the best accuracy from it. Chrome plating may open up groups 1 MOA at the most. Usually it's less than that. If you're just gonna use bulk, blaster ammo, there's no need to spend the extra dough on a match barrel. Chrome lined or not, 4150 CMV, 4140 CM or stainless steel, it will take several thousands of round to wear out a quality barrel.
Don't get wrapped around the axle about barrel profile. Really, the only danger here is getting stuck with one that's too heavy. However, I would choose what PSA calls a "lighter profile" barrel. It uses a .750 gas block ans has a thinner profile ahead of the gas block as well as under the handguards. The M4 and government profiles work but are made backwards as they are thinner under the handguards than they are ahead of the gas block. They are backwards because that extra material would be better located near the chamber where it can help deal with heat. The SOCOM barrel is thicker under the handguards to better deal with heat but is heavier. Basically, it's shooter's choice. I'd go for the lighter weight.
As long as you choose a quality stock, use what strikes your fancy. Magpul, VLTOR or standard M4. The Magpul MOE & CTR and the SOPMOD stocks are popular for good reasons. The Magpul MOE handguard is a good one to start with.
Pick a lower from PSA, Aero Precision, LRB, or BCM and you'll be fine. Folks tell me Spikes is good but I've never tried one. Billets cost more, must use more material for the same strength and are not good values.
Full auto carriers always work and bolts made from Carpenter 158 that are shot peened are good choices. You're probably gonna find out your carbine works best with either an H1 or H2 buffer so start with one of those. Choose sights to match the mission. Stay away from fancy controls like BAD levers until you've had a chance to shoot your carbine and determine if you even want one. The BCM gunfighter Mod IV charging handle is a good choice.
If you're a trigger snob, get the Geiselle SSA-E, SD-E or SSA. If a basic AR trigger works fine for you, get the ALG. Regardless of which of these you choose, you can easily sell it and get your money back if you don't like it.
The easiest choice in magazines is Magpul. Others work too but Magpul
always work right out of the bag.
A forward assist is nice but not necessary.
Don't over think it. Get good quality parts from trusted vendors and put your rifle together. Starting with a basic carbine means making changes later will cost less than making changes to a fancy configuration. Now, go build your rifle so you can get to shootin'