Revealed cylons cannot play skill cards as actions, but can they play skill cards as modifiers? i.e. if raiders are active, can I use strategic planning to give them a better chance to hit?
(Also, if I can't, then can I do this while unrevealed to make a big impact before I reveal)?

Revealed cylons are not affected by negative effects on crisis cards (using Caprica). Does this only apply to discarding skill cards/being sent to other locations? What about crisis cards that have something like the Current Player chooses someone to send to the brig? For example, on pass, Guilt By Collusion lets you send a character to the brig, whereas on A Traitor Accused, on a fail the current player chooses a character to send to the brig.

Revealed Cylons can "choose" not to be affected by negative effects on Crisis cards. So you would obviously choose not to discard, but you can definately send someone to the Brig if you are the current player in your scenarios.

Actually, the base game says that revealed Cylons are not affected by any of the effects of crisis cards, neither negative nor positive. Pegasus changes that to that they can choose to not be affected.

Actually, the base game says that revealed Cylons are not affected by any of the effects of crisis cards, neither negative nor positive. Pegasus changes that to that they can choose to not be affected.

Revealed cylons basically ignore all text on the cards, so no, you cannot play a Strategic Planning on a raider attack. But yes, you can while unrevealed if you're ready to give yourself away.

On Caprica crises, the cylon gets to choose anything that says Current Player chooses, so they would get to pick who to send to the Brig.