Well not much here to even critique...
Yes an 18" barrel reduces performance. A 20" barrel already reduces performance. Its a .308 so that caliber reduces performance vs a .260 or 6.5C in same platform.
When you say adjustable gas "plug" what is that exactly? Does Wilson Combat have a proprietary gas block?
What ambi safety are you running? Most allow the short arm to be swapped if you are a lefty and you could unbolt one side. I am partial to V7. V7 allows options of 90 degree or 45 degree throws on one unit with swapable long and short arms. Check it out and if you might want one my girl wants a single sided one and I have an almost unused ultralight I could part with cheap... V7 is kind of pricey on selectors.
For the trigger, I am now an all Geissele guy. I have 5, two G2S-E, two SSA-E, and 1 HiSpeed DMR. I prefer the 3.5 pound weight always, but it is not legal for a service rifle, though that does not seem to be your thing. I have tried lots of 2 stage AR triggers over the years (Knights, RRA 3.5#, LMT, Larue etc.) but I always come back to my Geissele.
For the bipod, if you want Atlas, get the short PSR bipod. Consider if you are going to do a full length ARCA rail at 6 o'clock and you may want the MPA ARCA biood adapter if so. Personally, I prefer a simple Harris for speed, weight, and the fact loading is less of a factor using that bipod. I also dont have a 6 o'clock full length ARCA rail yet (going on my current build) so I used the Larue Harris to reduce weight, height, and complexity while having a good QD (I have two). Your rifle will be heavy enough you may want to consider a different, lighter bipod option and consider an ARCA rail option. Certainly, in PRS type competitions, an ARCA rail you can infinitely adjust your bipod on quickly is a huge asset compared to a slow throw lever or fixed only options.
For an ambi charging handle I have a Raptor I like. I also have a Griffin Armament SNACH I like. I really dont like the BCM. You need to try them all and see what you like. Some work by left being independant unlock of notch and right staying still if worked on left lever but the right lever moves the left lever, so if you use the right lever both move. Some always move both levers together. Some allow you a solid, non-moving spot between levers to place your thumb and some have moving sections of lever in the middle of the charging handle while working it (which I hate since I press my thumb there to brace my hand). Some have very low hanging wide levers and some have a slim surface area for thumb... I like more surface area for my thumb. Some have aggressive texturing that is great with a glove but irritates your bare hand if you practice alot of weapon manipulation drills (my Raptor has is somewhat aggressive) Some are smoother/slicker so bare hands never get irritated (like my SNACH). Some have replaceable short/long arms you can swap, some are fixed so you better like it how it is. Some are symetric left right levers, some have a longer right lever. Some have a lever that goes to 90 degrees and stops, some go past 90 degrees and feel like your finger would slip. Really, its a personal preference thing. My two choices are Raptor and SNACH for ambi. I have owned 8 different charging handles. Currently have 5 different charging handles for single sided I have an old gen BCM which I like and a PRI Gasbuster I like.
Furniture is likewise a personal choice. I am slowly shifting to BCM Mod 3 grips. I think they are ugly. but love the size, angle, and feel. The tan color also does not match Magpul color. I wish I liked the MOE K2 grip more. I have found I dont like the rubber coated grips and I am slowly phasing them out. I dont know how many grips I have had over the years, almost all of them now that I think about it.
