Yes, there are 3 “editions” but the Legacy edition cannot be run outside of Rhino/Grasshopper and the honeybee_plus one is deprecated and only supported single-cpu radiance workflows.
Here is the documentation for the latest version of all the LBT core libraries:
https://discourse.ladybug.tools/pub/ladybug-tools-core-sdk-documentation
The diagram there shows you how all of the core repos/libraries relate to one another and gives you searchable docs for each repo/library. I should note that the core library dependency tree does not include the queenbee-python-dsl that @mostapha mentioned and you can think of queenbee as a layer above the core libraries, which allows you to write recipes using the LBT commands and Radiance commands in a manner that can be scaled to multiple CPUs. Once you have familiarized yourself with the latest core libraries, I really recommend getting to know the queenbee-python-dsl.