The Next-Gen Antivirus with XTP can integrate with Windows Defender ATP (Defender for Endpoint) because HEIMDAL's NGAV uses Windows Defender as a baseline engine.
This means that if you were previously using the Windows Defender ATP and you want to keep using it, you can have the HEIMDAL Agent's Next-Gen Antivirus running alongside and this involves NO additional settings in Defender for Endpoint if you are using the default settings.
However, if you are applying custom settings in Defender for Endpoint, Next-Gen Antivirus might not be able to enforce exclusions configured in the Group Policy settings.