Also, note how I mentioned GT6’s various energy units. Technically GT6 really only has one Energy System, which is made up of basically two values, the ‘size’ of the energy, and how many of the ‘pulses’ at that size of the energy (per tick).
Everything is in that energy system. Like you have:
- HU: Heat Unit, like a heater might burn coal to put out 16 HU/t, meaning it puts out a single ‘blast’/packet of size 16 of type HU out to its top face, and whatever is on top (if anything) consumes it to do whatever. HU doesn’t really have a “wire” block as of yet (much as a few of us keep saying that GT6 needs heat pipes like in real life, lol).
- RU: Rotation(Rotating?Rotational?Etc) Units, like a turning axle, the axle is basically the ‘wire’, transferring the packets of whatever size down to whatever receives it on the other end. This is why there’s no “backpressure” like there is in real life axle systems, it’s fairly simplistic.
- KU: Kinetic Units, like think pressure, or a hammer slamming down on something, like hydraulics in general is KU. I don’t think it has a “wire” either, though pipes transferring hydraulic pressure could make sense?
- EU: Electricity, etc… Normal metal wires
- LU: Light, distinct from heat, optical cables are its wires.
- QU: Quantum, used for mainly UUM
- Probably a few others I’m forgetting.
Basically various things run off a certain type of energy, and you produce a certain type of energy, and you’ll have a block or 4 converting between them. Something super common is trying to convert whatever you get to make steam, to send down pipes, to convert back to whatever else to drive something, as ‘steam’ has a fairly low loss compared to, say, EU, though EU is far more convenient so higher tier bases tend to use it just because of convenience even though steam is often more efficient (plus you can send a lot more ‘power’ down EU wires in large packets then you can steam through pipes).
This is why GT6 is an infrastructure mod, basically everything is just some pretty veneer on top of transforming types of energy between each other. 
And yes, from a code-side the GT6 energy is a single interface, not one per ‘type’, rather you just call or get called for a ‘packet’ of energy containing the type the size of that packet.