sharepoint online power user playbook is my first book going to launch very soon.
sharepoint online powershell
SharePoint 2019 feature id and feature list you can find out using powershell. You will understand basic powershell commands related to Get-SPFeature so as to get sharepoint feature id details and features related ot this sharepoint feature id. Follow step by step procesure to find out how to get sharepoint 2019 features id and features.