In this PnP Webcast, we cover what are the current customization options around the SharePoint "modern" experiences. This is relatively long webcast with multiple demos, since we wanted to cover different scenarios for the site and list customizations. We have also recently released new MSDN guidance around the customization options for "modern" experiences. This guidance will be kept up to date as we are rolling out new support scenarios.
Learn more on the Office Dev Center.