1984: For newbs, stick to Los Angeles-class. Once you can clear Beating The Odds single mission regularly then you can consider adding the Sturgeon/ Narwhal to the repertoire, trading speed for stealth and deeper test depth. Permit-class isn’t too bad either, if you can tolerate the 4 kt slower speed and slightly noisier noise output. Skipjack class is to be avoided unless you know what you’re doing because of its shallowest test dive depth, noisiest noise output, and only keeps 1 wire at a time.
For Missions, focus on Beating The Odds, Bastion Gambit, Steel Coffins, The Hunt for Red Bear.
Y2K: While the Seawolf-class is the quietest, has the most torpedo tubes with as many wires, and the most hardy against air-launched torpedoes (no joke, it may take anywhere between 3-6 air/ missile-launched torps to kill a Seawolf), I’m now preferring either the Flight II or Flight III Los Angeles-class. In one word, it’s VLS capability.
Because you need to stock extra TLAMs as insurance, and the Seawolf-class lacks VLS, you have to launch them through the tubes. This will count towards your final weapon count, and you will only be recalled back to Holy Loch/ Guam when there’s less weapons than tubes, greatly increasing the likelihood of having to do a mission underarmed.
VLS weapons do not count towards your final stock and can be fired instantly, at the cost of more limited launch parameters (less than 80ft depth, no more than 5 kts). Thus you can be recalled back to base with a full load of VLS tubes. The VLS also doesn’t get cleared out when having to stow SEALs onboard.
I myself like to load 10 TLAMs and 2 TASMs, with 4 MOSS, 6 Harpoons, and 4 TASM backing up the 2 in VLS, and the rest being Mk.48 ADCAPs. This gives me a lot more flexibility than the Seawolf class while being just as fast and stealthy, I would argue.
Missions: The above mentioned 1984 missions plus Junks on Parade and High Noon. Junks on Parade is substantially more difficult due to the shallow waters and constant ASW air support for the enemy, but can be satisfying if you can pull it off.