Joey, for the answer to your first question, just level a submarine crew. That will be your cloak and dagger. It doesn't matter what nation you use, all subs are great.
For the second crew, KM has the most range, it is basically the "snipe" nation.
For carrier play, again, it's personal preference. Ask 5 different people and you will probably get 5 different answers as to which nation is the best for CV.
As for crew setups, BB should be 2 main gunners, 2 AA gunners, 5 engies, 3 rep, 1 scout.
CV I will leave that to those who actually play one, and the same with the sub crew.
Hopefully that's more useful than steel_raven spamming his Youtube channel.