Of my four games, I have two games that are work in progress and I published them because I want community feedback/support, and motivation for myself to keep going. However, there's nothing to download yet.

The release status is set to In Production or Prototype, that makes sense. But I wonder if I'm using itch correctly, it seems to want a download and I don't want to turn off users who come to my page expecting a game to play.

Also, when I do finally release the game... switch it from "in production" to "released"... am I gonna get the same bang for my premiere as if I had just released a new game at once... top of most recent listings, a spike in popularity for new users just discovering it and so on? Is it worth starting a whole new project for when it is finally ready?

Those are good questions and I've been pondering the same things myself at times. If you don't have anything downloadable/playable yet, you can just do a devlog on either the Devlog tab or in the Community forum and keep your audience updated about changes and then create your game page once you have a demo.