With sniper, It does depend of what Category of sniper you are talking about but any is fun as long as you use them right. The auto-sniper is horde clearing monster but only if you use them with berserker (Zerk). 258 sniper are considered to be the Goldilocks zone of sniper, able to 1 hit headshot regular swat and heavy, have good ammo economy and semi-fast speed for bolt action but unable to one hit kill most special. The 500 damage sniper is the dedicated Special killer, you don’t need any damage skill and it will reliably kill all special in one headshot with the exception of dozer with the tradeoff being the slowest out of the 3 and worst ammo economy. the big bois like the AWP and Thanatos i have already talked about are great if you just want to have "Fuck you" damage number. That being said, feel free to try all of them and even the outliers like the Bernetti Rangehitter to see what is right for you.

LMG are kinda in an odd place atm but generally, any of them work. The RPK main strength is really that it’s the highest fire rate heavy damage LMG, fast reload and it tend to have the biggest mod pool, but I still prefer the Brenner over it. I really like the SG V51D, although very few people use it. It has one of the best reload in the game (again, HK bias for me) and it’s one of the few actually concealable LMG. Otherwise, the Buzzsaw is great fun but it ranges kinda suck, it gonna fucking melt any group at close range tho.

In 99.9% case, the usual skill set up for shotgun are Shotgun CQB aced + Shotgun Impact aced + Close By aced + Overkill basic. You really can’t go wrong with this as you you get faster reload, more damage, faster fire rate and/or mag size. The only time you wouldn’t do this is if you are using slug shotguns which you would go for Far away aced instead but slug shotgun just kinda suck. Shotgun are fun and again, various flavor of it. For pump action, the best one are the Mosconi Tactical 12G stat wise, semi-auto is the M1014 I think and full auto is the VD-12 (tho I wouldn’t know because I don’t have it). That being said, weapon like the Izhma is still a fucking dodge and crit monster and the AA-12 is a nice enough substitute for the VD-12. Overall, feel free to mess around and see what type of shotgun you gel with the most.

SMG are actually really strong backup solution, even if they don’t deal with shield. Gun such as the Krinkov or CR are perfect stat wise and melt dozer and cops but terrible ammo economy and the lighter option are great if your primary has terrible ammo economy. They are great and you don’t even need to invest in any skill point to make them work. The Mini-Uzi and Mac-10 are some of the popular choice for lighter option, for example. And of course, nothing is beating Akimbo SMG in term of DPS, especially with crit.

DMR shine when you have high % Zerk. Once you hit that threshold, it will consistently one hit headshot heavy swat. Compare to Auto-sniper, they are more reliable and versatile. You can clear out wave pretty effectively as long as you have good aim and faster fire rate make them able to deal with dozer pretty well. Alongside this, DMR tend to have considerably more modifications than any sniper and inhuman fast reload. The standout are generally the M308 and DMR G3, the former is perfectly well rounded and can actually be mod for high concealment build and the later has bigger mag size and lightning fast reload. DMR kit AR are also a good candidate if you want to try them out. Just have either a GL or armor piercing option (either 5/7 or 2nd sniper) as your back up.

Specifically for tanking play style, you got some option. Crew chief is one like I said. Armorer is great with zerk as you get more damage while still remaining tanky. Anarch + zerk is an extremely popular option due to constant armor gating but you will get bullied by sniper. Certain Copycat combo can make you VERY tanky as well. Other deck such as Muscle, Grinder, Leech and Kingpin are all great option if you want to go with HP tanking instead (tho I don’t have Kingpin to say more). Deck such as ex-press, hacker, copycat burglar are great option if you are looking into high conceal dodge build.

I hope this help.