
Hello
Microsoft personal and business products are two separate ecosystems, so, if you have a Microsoft 365 personal subscription and a business subscription, then they are two separate accounts and two separate products.
If you cancel the personal one, you could lose files and emails that take up the additional space beyond the free alllowed storage, but you would ave a grace period to download them.
If you cancel the business one, you can end up losing access by te end of the subscription and lose all files/data.
Regarding the constant prompt for password, it was a bug from a while ago but that bug was short lived. Are you the admin user for your business account? Do you have MFA set up for that account?