How would you rank them in terms of bang for the buck in reducing recoil and muzzle flip in 5.56?*
Overall weight
Muzzle brake
Gas system length
Adjustable gas block
Buffer weight/springing
BCG weight
Cartridge load(5.56)

Which are the trickiest to implement in terms of reliability? What to avoid completely unless it's a range plinker?

What are some examples of your builds/experiences?

What is the delta between a completely trick USPSA match rifle and a more mainstream build, for example a 16" carbine gas M4 barrel, carbine buffer with an A2 flash hider for comparison?

* Fully acknowledging my sissy status, lack of practice, technique, understanding, testosterone and likely commie polluted precious bodily fluids. Thanks.

I have a 18" and 16" that still carry A2 cage. They are mounted with NF optics and are merely bench rifles so all I put in them were H2 buffers.

My, "go to" rifles are what I care about as far as muzzle control is concerned.

One is a 16" carbine length system. Purchased it from a local manufacturer. Over-gassed so much the ejections were at 1230 and very snappy.

After a drawer full of springs and buffers, I settled with JP Enterprises H2 Silent Captured System. That coupled with a  Ultradyne Apollo muzzle brake completely calmed it down. Smooth as butter and stays right on target.

The other, "go to" is a 11.5" (pistol for a few more days). It was snappy, as well.

Strike Industries JCOMP for the muzzle and a Geissele Super 42 H3 did the trick.  JCOMP is small and not too obnoxious.

Proper technique > hardware.

After that, muzzle brake.

This. For a huge % of people, their fundamentals aren’t good enough to warrant it for recoil control and will just snowball the bad technique if/when they go to larger calibers. Don’t get me wrong, they make a difference. Just saying for most people a standard A2 is perfectly fine.

Now setting your gas system up for ‘just right’ can make a pretty big difference. Probably more expensive though, but lets you be more variable with muzzle devices later instead of being locked into XYZ for performance.

Best bang for your buck would likely be an effective brake.  Effective brakes are loud/punchy, and usually exhibit pretty bright muzzle flashes though, so there’s no free lunch.

Gas system lengths are meh to a certain extent.  A MLGS barrel with a hogged out gas port is going to be worse than a CLGS barrel with an appropriately spec’d port.  Apples for apples, the longer gas system is seeing less pressure, but gas volume has a vote as well.

Outside of that I’d probably say an AGB, and if you really want to fine tune to the ragged edge of function, LW reciprocating components.  You’re giving up reliability in adverse conditions, though, so take that into account.

As others have said, a good muzzle brake will give you the best ROI as far as parts go. Be advised, if you’ve never used one, that they are extremely loud and concussive and not what anyone would recommend for any kind of self defense role.

Have you considered a better recoil pad? Limbsaver makes pads for the GI M4 stock and most Magpul stocks.

What I have now is a 14.5 mid-length Faxon pencil barrel with a lightweight MI M-Lok hand-guard, a VLTOR A5 buffer system/B5 SOPMOD. It has the Faxon slim flash hider to bring it to 16.5 OAL.
Recoil impulse is very smooth but I get a lot of side to side yaw and a little more muzzle flip than I'd like.
Is there a muzzle brake option that's not too obnoxious?

I shot USPSA 3 gun for about 20 yrs... the upper is a RRA mid length gas medium weight 1/8 twist barrel that shot M193 pretty much exclusively for the first 15 years... a lot of S&B with NATO circle cross head stamp would shoot 5" at 400m...it has a clamp on gas block that was not modified (reliability), an M16 bolt carrier that shrouded the firing pin and RRA bolt that had a SOCOM bolt upgrade of ejector spring and "O' ring ... I did not use the McFarland style ring as I shot cheap Wolff for local matches, and the Wolff would carbon up badly at about 100rds, and effect reliability... the stock was a Viet Nam era A1 with a rifle length buffer tube and Enidine hydraulic buffer, Hogue pistol grip, and small diameter Midwest Industries fore end...

the muzzle brake was a collaboration with a shooting friend that was an M4 project manager at SOCOM and edited the SOPMOD manual... I fully threaded the boss of the Miculek brake to delete the locking nut, and continued the minimum diameter drill bit to thread 1/2x28 through the rear wiper... we both considered that this modification made a noticeable difference is smoothing out the recoil impulse... it was clocked with shims to approximately 1:00 to control some dot shake... a 4x32 ACOG TA01 and later a TA31F was used as I liked the ability to use the stadia lines to hold for wind hold off... I managed a 12th place stage finish on the sniper range at Ft Benning in 2009, at 62 years of age, before cataract surgery....I switched to Australian Outback 69 Sierra match kings after the Ft Benning matches for Area 6, anything past 200m got the match grade ammo as my lot of S&B had run out and other M193 did not have the accuracy...

muzzle brake, rifle length buffer tube with hydraulic buffer would be my suggestions ... trial and change clocking of brake to help eliminate shake, though I did more work getting an AR9 to eliminate shake than actual recoil reduction, because I could control cartridge velocity better...

Lead weights are probably the most cost effective.

Flip - cheapest help is a LARB buffer cap or similar. More expensive is a hydraulic buffer.

Side to side is likely shooter mod. Or receiver fit.