Exposure Compensation adjusts exposure of the camera auto modes, like A, S, P, and Auto modes. It does Not change camera Manual mode exposure, however, it does still affect what the light meter reads and shows, perhaps guiding you to adjust manual exposure yourself.
Flash Compensation adjusts metered TTL flash exposure. It does not affect manual flash. Manual is manual.
Auto ISO does affect camera exposure, including camera Manual mode exposure, and does affect TTL flash metering. Manual flash cannot react to Auto ISO changing, and Auto ISO will stay at Minimum ISO if camera recognizes a manual flash is present.
There may be multiple places flash compensation can be specified (on flash or on camera for example, or in Commander menu if used), and they all add to a total.
On Nikons, Exposure Compensation also adds to Flash Compensation so that TTL flash reacts with the sum total. However, newer models, including D7200, has a new E4 menu to either do that add (EC + FC), or not. Canon models for example, do not. Pros and cons either way. Your choice.