Hi @jin, welcome to the Community!
Glad you’re trying Papyrus out! 
If you’ve got a work-in-progress book you want to bring in, you can turn a Word (.docx) into a Papyrus file with the Start Screen’s “Import Project” feature.
Thanks for your thoughtful question! Right now, there are no plans for a different pricing tier like you described, but we’re listening and really appreciate your feedback. 
Makes a lot of sense. Having the tools sorted out helps keep the focus on writing.
There’s a huge amount of features for different stages of writing, all the way to the publishable output.
You mentioned you just started writing, but if you want to play around and see your text in different publishable versions, try out the Book Designer. You can do different trim sizes, try out headers, footers and all things layout!
You can also print out PDF outputs with the PDF export button in the toolbar.
Have fun with Papyrus! 