The Greddy blue box is an untunable controller that acts as a 'piggy-back' to your ECU. The VAFC/SAFC are also piggy-backs. These allow you to make minor adjustments to fuel trim and timing (I think). They are not as detailed or tunable as a full EMS.

You can use these tuning units with NA or FI. You are more likely to need them for FI because the OEM computer was not made to account for boost and run correctly with that upgrade.