I'm gonna list my top 3 ARs for this AR dominant game after 6 days of playing. I guess it could change later with patches, but without weapon re-balancing, these will be the top dogs:
1. MSBS (with silencer + red dot or silencer+full auto)
2. Remington R5 (with silencer + red dot)
3. AK-12 (with foregrip + muzzle brake)
The Remington feels like the ACR from MW3 and MSBS feels like the M16 from MW2. AK-12 feels like AK-47 in general.
IMO, These guns make all the other assault rifles irrelevant, but we all knew this day was coming. I really like the Honey Badger because it
doesn't give a shit and eats larvae and cobras and shit, but I'm not a fan of the damage. Some weapons are simply better than others. This is COD after all.
For assault rifle perks I highly recommend using quickdraw+focus as your base and then add whatever you want according to your play style. This is another reason why the assault rifles are the best because you don't need to spend all your points on a ton of specific perks just to make them good.
Shotguns
I've been using something similar to the SMG perk setup further along in this post, but only on the smallest maps in the game. I just wanna say this right now: Good luck sneaking up on anyone, ever. Pray for a revenge spawn so you can shoot them in the back. With the SMGs you can at least get some shots in from range. I mean they're basically long range feathers hitting them, but at least your bullets are reaching them with an SMG. With the shotguns, the only satisfaction you get is the other person knowing that they just got killed by the worst weapons in the game. I guess that's good enough.
Snipers
I like the L115 or USR with quickdraw and focus perks. USR with chrome lining attachment and L115 with armor-piercing.
Marksman Rifles
I like MK14 with 3 round burst, quickdraw and focus right now.
Pistols
Magnum could have been awesome, but they limit how fast you can shoot it, so I just use the M9. The pistols in general are horrible in this version.
SMGs
If you have an overwhelming thirst for SMGs that absolutely needs to be quenched or you will die, then try either the Vector or MTAR-X. They're decent, but you will be at a disadvantage on these bigass maps at all times because MSBS/Remington is gonna bust out the lubricant and have a party in your bumbum as soon as you're spotted by anyone.
Just like the assault rifles, you should try to use the focus perk on SMGs at all times. Quickdraw you don't need as much because these guns already ADS pretty fast. You need to spend your points on a shitload of perks and use the specialist package to make this class work. I recommend using a silencer and the following perks:
Ready Up
Sleight of Hand
Agility (not mandatory, but helps)
Marathon (if the map is small, you can replace this with ping)
Takedown (good for flanking)
Dead Silence (also good for flanking, but you can still be heard by amplify users which leads to people camping and listening)
Resilience (depends on the map)
Focus (this should be used on most guns)
Specialist
For the specialist streaks in general, I recommend putting scavenger at 3 and then for 6 and 10, put expensive perks like deadeye, off the grid, wiretap etc. Once you get to the specialist bonus at 12 kills you don't get all the perks like in MW3, so it's been heavily nerfed. You're limited in what you can get for specialist bonus, just choose wisely what perks you want in there.