Apple One - problem with 2 Apple IDs

I have 2 Apple IDs, because I created my iTunes account (@sonic.net) long before iCloud existed (icloud.com). I have an Apple Music subscription on my @sonic.net Apple ID, and all my apps, songs, movies and TV shows have been purchased with the sonic.net Apple ID.

Using my sonic.net Apple ID, I signed up for the free trial of Apple One.

When attempted to associate my existing iCloud storage @icloud.com with Apple One, I got an error "You must first cancel your iCloud subscription, then try again." But when I attempted to cancel the iCloud storage on my @icloud.com Apple ID, it turned out I have an annual subscription until September 20201 that cannot be cancelled or downgraded.

AppleCare support suggested go into the App Store, log out of @sonic.net Apple ID, and into my @icloud.com Apple ID and subscribe to Apple One. Then they suggested I log back out of the App Store, and back into my @sonic.net.

But what they couldn't answer:

• Would I then have 2 Apple Music subscriptions, @sonic.net and @icloud.com?
• Would I lose my @sonic.net downloads from Apple Music?
• What would happen to all my apps, shows, and iTunes purchases?

Ultimate, I just cancelled my trial Apple One subscription. Until I can get a definitive answer how to keep all my content if I subscribe to Apple One on a different Apple ID than my App Store Apple ID, I'm not comfortable with potential data loss.