How can I fully customize a Hydrogen site using a custom theme?

[sdinkler]

Hey everyone, looking for some guidance.
I've been tasked with porting over our Shopify website to the new Hydrogen framework for the increased customization options it offers. However, we also want the Hydrogen site to be fully customizable (images, menus, text, etc, not necessarily formatting). 

I understand the fundamentals of setting up the Hydrogen store and getting store data using GraphQL, but am a bit hung up on the customization options. Would it be best to develop a new theme from scratch in order to accomplish what I'm trying to do, or to just grab elements from our existing theme and port them to the new Hydrogen site? Is every aspect of the theme accessible through GraphQL? For instance, I am definitely able to grab the main-menu links and map those to the new site, but aspects like the image carousel and the highlights banner don't seem to have a set label that I'm able to grab through GraphQL.

It seems like developing my own theme as just a sort of database in order to create a customizable Hydrogen site is the best option, but I'm assuming I lose the Live preview on the theme editor if I attempt to do so.

Any assistance to help me wrap my head around all this would be helpful. Thanks for reading!

[nhcon]

Curious if you found any help with this.. Thanks

[sdinkler]

Unfortunately no, I've just ended up making it not nearly as customizable as I wanted to.