Equine Functional Taping and OIO Biomechanics are not different levels of the same thing. They are different modalities built for different outcomes, different practitioner needs, and different stages of training.
If you want horse-specific functional taping you can use across a wide range of cases, EFT is where most people should start. If you are a qualified practitioner ready for advanced biomechanical assessment and structural taping, OIO is the next-level path.