Is there a list of the built-in plugins & more in detail description?
There are a lot of built-in plugins. Many are obvious given the name and short description.
But some are fairly terse, and even if you know what it might do there’s no information about how to use it or what it really adds.
I’m afraid you’ll find out that the one downside of UE4 is the documentation. Most of the time to know how things actually work you have to go to the engine source code and learn from that. The documentation is very barebone, it reminds me of a Doxygen generated doc and nothing else (probably it is!) The only reliable resources are the videos and live streams UE4 produces, with samples, demos and the like. It’s no documentation, but that’s all we really have.