Hi,
Currently evalutating if XWiki is a better fit than Liferay for my needs. Liferay is quite bulky, and I really only need Blogposts/Wiki/Pages.
I was wondering what the difference is between XWiki and Liferay? Or CMS and (Second gen) Wiki?
cool! I don’t know liferay so can’t answer but once you’ve got to know XWiki well, I’d be very interested in a write up/forum post about what you think are the main differences 
Re wiki vs CMS, I know this page: Alternatives - XWiki
IMO the main difference is philosophy and wiki is focused about content first and authoring content collaboratively.