The past.
Please do not compare the 767 Captain III fidelity to our previous products.
The 767 is meant to be different: great visuals+essential systems and a flight model, all for a fraction of our regular airliner price.

The present.
Some of  the 767 systems are coded from scratch, but some (e.g. FMC, MFD, PFD) are stock. However it's not a mod of the 747 code, it is your current local 747 code plus an extra CS code which provides compatibility with CS 3D models. That's why you see some features of the 747 like 4 engines, 747 naming etc. Well, that's what the Essential functionality paired with default 747 systems simulation is all about.

Third party mods.
Hardcore simmers may enjoy free community mods. Some of them are quite advanced. We do not support the mods setup and compatibility issues.

The future.
We are not going to make any improvements of the default 747 code. So the 767 Captain III is pretty much done systemswise. We will address teething issues so please feel free to report them.

What about a "study level" 767 in the future?
Possibly, but it's going to be a 767 Captain IV, if any.