Which wallet do I use — in the browser and in the launcher?

It depends which one you are in:

• In the launcher — the built-in wallet. Set it up once from the wallet screen: choose a password of at least 8 characters, then either create a new wallet or import an existing one from its seed phrase or private key.
• In a browser — the Creta Wallet browser extension, for Chrome and other Chromium browsers. The extension cannot be used inside the launcher, which is why the launcher has a wallet of its own.

Your account stores the wallet address you are currently connected with, and that is shared across Creta apps — so connecting a different wallet in one place changes which address the others see. Importing the same wallet into both the extension and the launcher keeps everything on one address.