Shortwave will wipeout your account and all associated data upon request — you can do so from settings on desktop & mobile. This will not affect any messages stored in your Gmail account. You can also revoke Shortwave permissions from your Google account here. Learn more about how Shortwave takes your security & privacy seriously.
If you choose to try Shortwave in the future, all you have to do is sign up again via Google sign-in. For further questions, reach out to email@example.com