Hi, I understand you want to keep work and personal profiles separate, but the issue is that your work email isn’t a personal Microsoft account, it’s tied to your organization’s Azure AD.
Windows can’t create a new local user with that email unless the device is joined to your company’s domain or Azure AD.
The easiest fix is to go to Settings > Accounts > Access work or school > Connect and add your work account there or create a local account for separation.
For OneDrive, make sure you’re using the OneDrive for Business app and signed in with your work account, not just creating a folder manually, because that won’t sync.
Quick question: is your PC currently managed by your organization or just a personal device?
Regards,
Aron