You can use a Restricted page mode to have a private page with private files that are only accessible to people you create access keys for. Or, if you want your page to be public with limited access to downloads, you can can set your project page to Public, and check “Disable new downloads and purchases.” You can then generate download keys to give people explicit access to the files.
Example:
Generally, I would opt to have the public so you can let people who don’t have access to the game still learn about the project and follow it for when it’s.
There currently is no good way to have a hybrid, some files available others not approach. You can kinda make it happen using Demo files. This is something we’d like to address in the future.
Hope that helps!