Things are a little all over the place with 4.26 help files/docs, can someone please clarify?

I want to know if there are project sample files for 4.26 water, the ones with Niagara and foam and the rest showcased by Epic.

Did these make it into the content examples yet? Where can they be found?

Also is there some serious documentation on all this somewhere yet?

On another note: Niagara has been out as production ready for a while now but I am finding it hard to wrap my head around its node based approach coming from Cascade (which is much more artist friendly), I need some resources which explain what each node does specifically and their functions in practice. Are there any good resources out there for a step by step explanation of its features with good examples?