I don't have a Groove Pass subscription, but I do have my entire music library backed up to my OneDrive storage. The Xbox Music app for Windows Phone 8.1 had an option to turn off streaming, but I can't seem to find a similar setting in the Groove app for Windows 10 Mobile. I prefer playing music from local storage rather than streaming for two reasons:
1. No worries about the stream being interrupted in low cellular coverage areas or when going out of range of Wi-Fi.
2. I can control what music I have synced with my phone while leaving the OneDrive music library as is. I typically shuffle all music, but don't want to hear Christmas songs mixed in out of season, which happens often when streaming music from my OneDrive collection.
1. No worries about the stream being interrupted in low cellular coverage areas or when going out of range of Wi-Fi.
2. I can control what music I have synced with my phone while leaving the OneDrive music library as is. I typically shuffle all music, but don't want to hear Christmas songs mixed in out of season, which happens often when streaming music from my OneDrive collection.