Refund after signing up?
If I already paid a years worth of Apple Music will I get some sort of refund after signing up for Apple one?
Bundle Apple subscriptions with Apple One - Apple Support
If you already subscribe to Apple Music, Apple News+, Apple Arcade, or
Apple TV+, you don't need to cancel those subscriptions. They will
automatically be canceled when you're billed for Apple One.
but it doesn't talk about refunds yes/no for most of those. Another link does talk about iCloud refunds though.
What happens to your iCloud storage plan when you sign up for Apple One - https://support.apple.com/HT211784