I will definitely give the M67 Mags a try, I like the sound of going semi-auto but not the idea of dropping down to 10-rounds, I definitely like the idea of 1 hit kills, of course, I have to get that hit in the first place, lol
To reiterate, I used the M67 mags for Hardcore because it was 1 HTK in Hardcore - they're a 2 HTK for Core inside 50m and a 3 HTK outside that. So the M67 mags really aren't good for Core because they only lower your HTK by 2 but lower your ammo capacity from 30 (or 45) to just 10. In Hardcore however, the CR-56 is only a true 1 HTK inside 35m - outside that you'll likely need 2. The M67 mags ensure it stays at 1 HTK for all ranges to any part of the body.
I won't lie, I don't know what I am doing when it comes to attachments half the time, what I do is read what it says, and hope it will help with hitting my goal.
Solo NVG has magnification, helpful for getting those 100 longshots and the night vision also helps pick out many of my opponents from the background and does well through smoke dropped by opponents, except for those running cold-blooded.
45 Rounds because spray and pray, Sleight of hand because I need frequent reloads on account of spray and pray.
Compensator because it helps reduce that barrel climb when I panic fire and forget to use bursts (nearly all of the time).
A couple comments here. I get why you like to use the Compensator - over 25% reduction to recoil. I personally still use a Mono Suppressor in Multi-player for 2 reasons. The first is I HATE when the other team knows where I am - I will use a suppressor over anything else almost all the time. And secondly, I basically only use Multi-player to unlock attachments/camos for Warzone - Warzone is my priority. And in Warzone the Mono Suppressor is an absolute necessity, so my logic is...if I can't use the Compensator for 25% recoil reduction in Warzone, I shouldn't "practice" that way in Multi-player either. If I practice with reduced recoil in Multi-player, then when I try to control a spray in Warzone the gun will feel like it has 25% more recoil and I won't be used to it.
As far as optics, I'm not sure if you're aware but there are quite a few optics that actually reduce a bit of recoil (for some reason). The Solo NVG is actually one of the better ones for overall vertical recoil reduction (15%) but it doesn't do anything for side-to-side stabilization. The VLK does 10% for both vertical and horizontal. The Cronen C480, Merc Thermal, and Scout Combat are all good for recoil reduction as well. For a brief comparison between these 5 sights:
Solo NVG: 3.25x zoom plus the thermal overlay which helps with target identification. Also reduces vertical recoil by 15%. The downside is a 25% ADS speed nerf.
VLK: Only 3.0x zoom and doesn't have the thermal overlay, but reduces both vertical and horizontal recoil by 10%. Also the ADS speed nerf is just 8%, 1/3 of the NVG.
Scout Combat: 3.25x zoom like the NVG w/o the thermal overlay. Can't find hard numbers for the recoil reduction, but the plots seem to indicate it could be 15% for vertical like the NVG as well as 10-15% for stabilization like the VLK. It also is good for ADS, with just a 9% nerf. So it is very similar in overall performance to the VLK, however what it does lack is a clear sight picture - the VLK simply has the prettiest sight in the game while the Scout Combat clutters it up.
VLK Scout Combat / Cronen C480
Cronen C480: Offers 3.5x zoom again without a thermal overlay. Offers what looks like a similar 10% vertical recoil buff and mayyyybe 5% for horizontal stabilization. So more zoom than the VLK with less recoil buff, it has a simliar ADS speed nerf (10%). However it also has the ugly Scout Combat reticle pictured above, so again I'd give the edge to the VLK.
Merc Thermal: 3.25x zoom and a thermal overlay like the NVG. However it offers a 10% vertical/horizontal recoil reduction like the VLK, plus it has a clearer reticle than the NVG (in my opinion).
NVG Merc Thermal
The issue with the Merc Thermal is, like the NVG, that thermal overal comes at a cost - 25% ADS speed nerf. Your ADS speed is slowed 3x more than the VLK, Cronen C480, and Scout Combat while offering similar zoom and recoil reduction. So basically you're paying for the thermal overlay with about 50ms of ADS time. I personally don't use thermals because of that slow ADS nerf, and I don't like the idea of missing the occasional target because they had Cold-Blooded equipped. But I do acknowledge that the thermal overlay does have it's uses especially around smoke.
Now as far as Sleight of Hand. Different sources measure reload times differently, but according to XclusiveAce the CR-56 goes from 1.69s to 1.10s reload time with Sleight of Hand equipped. That is definitely not insignificant by any means - that is a 35% reduction. However you have to do a cost-benefit analysis with the other attachments you COULD be using instead of Sleight of Hand, to see if anything might offer more benefit.
Laser: I don't know how you play, in terms of run-n-gun or more passive medium range play. But the Tac Laser cuts off 15% ADS time, which would wipe out the entire additional penalty your NVG thermal gives you, while also offering some additional aiming stability. I use a Tac Laser on any weapon I am not planning to hard-scope with, since that makes the laser visible. This means I wind up skipping the Tac Laser for a lot of my Multi-Player classes because I do like to stay back and keep most encounters to medium range if I can, so I wind up pre-aiming sightlines quite frequently. I will also mention, if you like to run-n-gun the 5mW laser offers a huge buff to your hipfire and "sprint to fire" time, meaning you can hipfire faster after coming out of a sprint.
Stock: Names can vary weapon-by-weapon but for the most part each weapon has 4 stocks: a Stability stock that buffs Aiming Stability while nerfing ADS strafing speed, a Strafing stock which does the reverse - boosts ADS strafing speed while nerfing Aiming Stability, an ADS stock which buffs ADS speed while nerfing Aiming Stability, and usually a No Stock that adds a Movement Speed buff and Recoil nerf to the ADS stock. The CR-56 has all 4 of these options, plus a couple others. Again this would depend on your playstyle. Since I prefer mid-range gunfights, I like to equip the Stability stock (the FTAC Hunter for the CR-56). Especially for Hardcore, ensuring your first shot is accurate is paramount, so the added Stability is worth losing ADS strafe speed. However if you prefer to run-n-gun more than the ADS stock (FSS Close Quarters) or No Stock might better suit you. However I wouldn't pair the No Stock with the Intruder barrel, as your recoil will go to crap because both of those will combine to lower your recoil control by nearly 50%.