Event = raw material (mnemonic: a wedding is an event = hours of film, thousands of photos)
Project = the movie you make (mnemonic: "My next project will be even bigger!" = a selection from the raws
Library = a collection of all Events and Projects,
Just two Libs seems to me too 'narrow'.
Don't know how you're organized in real life… Theoretically you could make a Lib per client. Or, a Lib per 'theme' (cooking, watches, collectors items...). Keep in mind: you can 'close' Libs (and re-open) = less clutter on screen, no need to scroll the work of years...
Keep in mind, FCPX has an awesome organization tool: keywords and smart-list. Just dumb your material into an Event. Then select all clips** with the same keyword and drag's onto your Keyword Collection - done, You can give a clip several keywords, those 'markers' can overlap, etc ...
And no need to manually organize by meta-data … (don't manually rename clips, pushing into folders etc.)
Invest 20$ into Lesson for Final Cut* (<<< link to US AppStore) from rippletraining.com. Steve&Marc explain those tools within minutes
* I dont profit from mentioning this, just a satisfied customer.
** I say clips - means stills or sounds too