Welcome to Librarium Online!
Just a quick thing I am having problems finding the rules for the craftworlds. Do they exist anymore such as the ghostwarrior craftworld?
No they don't sadly
You can still build themed armies, but no codex special rules exist for them anymore.
There may be unofficial or even official rulesheets for craftworld armies out there, but you would need your opponents permission.
More specifically the way you'd pretend to be them is to use the now always availible rules for taking wraithguard as troops and for spiritseers, which used to be only their things.
I was a Biel-Tan swordwinds player for years. I love a fast aspect warrior army. I hope they either re-release the rules or do what they did with marines and allow different choices depending on your HQ.