Overthinking It - Clean Installation

I have been upgrading my site since 2012, and have a lot junk hanging around in the background, so I am going to do a fresh installation. Which I am working on in a development site.
When the old information is brought across before I go live, what actually comes across?
I know that the products sales etc will be bought across, but do I have to re-do all my pages, payment methods, shipping and taxes etc, or do they also come across?

Thank you for all your help