Quick answer
When you install and authorize each app, the app will list the information which they are requesting access to and the actions that it can take on your behalf (e.g. leaving feedback for you).
If you uninstall an app, that app no longer has access to any information related to your Reverb account. Apps should never ask you for your account password and will never have access to sensitive data such as your password, bank account information, or PayPal password.