Regarding first order, in addition to Kru, Kylo and FOE, the classic FO composition also includes FOO and FOST. That said, it's difficult to recommend a single team, since Hux and Sith trooper have recently been added and another Kylo will be added at some point, so no one knows what will end up as the best FO team a few months from now.
For your Darth Revan team, you need SE Trooper. Other than that, a good plug-and-play character like Thrawn is a good idea, until you have Malak.
For your Traya team, zeta Count Dooku works well. This can also be good place for Thrawn. Anyway, regarding Traya, Sion, Nihilus, Dooku, Palpatine, Vader and various other empire and sith characters, they are best to mix and match, depending on what you need them to counter.
For your Padme squad, I don't think a low star C3PO is much of a problem, since his abilities are what make him good, and his stats usually aren't the issue. Barriss is decent on that squad.