Big questions people need to answer for themselves when going this route are:
1. Is a clone the most important focus? If so, am I willing or able to:
a) address both the cost of some unique parts (KAC FF RAS, unique ARMS rails, small parts)
b) go with older ARMS QD rings vs modern rings?
c) still have money left for the suppressor and optics
2. Do I want the ability to clip-on thermal in front of the day optic for hunting/night shooting?
This can be done with the Mod 0 with ARMS 38 SPR Top Rail, non PEQ-2 option, the Mk.12 Mod 1 with KAC FF RAS, and the Mod H depending on scope height/Clip-On base height for optical alignment between the day and clip-on tubes.
3. Do I want compactness for maneuverability or do I prefer more of a range and tripod precision carbine?
For a compact direction, the telestock variants are the way to go obviously, with the LMT SOPMOD being the most common stock for that. The most compact overall length option among the Mk.12s/SPRs is the Mod H with a telestock, since they have 16” pipes vs 18”.
I’m more of a fan of the pre-SPR JSOC and USASOC Sniper carbines since they don’t really sacrifice compactness, and still deliver all the precision you will need with correct barrel sourcing. They had shorter gas systems though, which don’t run as smooth as a RLGS SPR, but it’s 5.56 so not really an issue when dialed-in with the suppressor.
From prone and other supported positions, I’ve found the RLGS 16” and 18” suppressed SPR variants to be one of the smoothest and pleasant shooting experiences you will ever have, so there is a lot more merit to the performance of these weapons even when you go full clone correct.
Best thing to do is buy your Allen Engineering suppressor now, get it transferred to your dealer, and start the infringements with GayTF paperwork. That’s your biggest bottleneck after the KAC RAS if you’re going Mod 1 route.
Another thing to consider is the Mil-Std conformance of your critical core parts, namely the BCG, barrel extension, and LPK. You don’t want one of these modern nitrided BCGs with loose tri-bore dimensions, a run-of-the mill bolt, and weird parts imported from some place in the Pacific. Get Colt or FN parts for durability and a set of TDP compliance on them, although I’m not a fan of the High Pressure Test requirement on the bolt.
