I can see the description of the Settings in the Metadata API Developer Guide, as well as a way to retrieve these for an existing org.
However, I don't know how to get the values defined for the Features for a specific org. Is there a way to get them using an API, to know what should be set in my definition file to match a specific org ?
The features listed in the DX doc is the following one:
Supported Features You can enable these add-on features in a scratch org: - API - AuthorApex - Communities - ContractApprovals - CustomerSelfService - CustomApps - CustomTabs - ForceComPlatform - MultiCurrency - PersonAccounts - SalesWave - SControls - ServiceCloud - ServiceWave - Sites