You can compare current and pre-Pkg3 docs. TL;DR: LOAD_PATH used to be part of the recommended workflow, and for most purposes these uses have been superseded by the new Pkg workflow. LOAD_PATH is still there but it is no longer something users would modify routinely.
In the discussion above, for example, with multiple people telling you this. A lot of the documentation is catching up about these things, and there are WIP issues, but the idea of using projects to organize your code has been around since the first JULEP on the issue.
I think you are approaching this wrong. We are not talking about how to interpret a fully specified standard, but solving a problem in the context of the current code loading and Pkg features, some of which are WIP.