Your configuration is passed down to the provider. (e.g: `new AWS.S3(config)`). You can see the complete list of options [here](https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/S3.html#constructor-property)
See the [using a provider](https://docs.strapi.io/developer-docs/latest/plugins/upload.html#using-a-provider) documentation for information on installing and using a provider. And see the [environment variables](https://docs.strapi.io/developer-docs/latest/setup-deployment-guides/configurations/optional/environment.html#environment-variables) for setting and using environment variables in your configs.
Due to the default settings in the Strapi Security Middleware you will need to modify the `contentSecurityPolicy` settings to properly see thumbnail previews in the Media Library. You should replace `strapi::security` string with the object bellow instead as explained in the [middleware configuration](https://docs.strapi.io/developer-docs/latest/setup-deployment-guides/configurations/required/middlewares.html#loading-order) documentation.