Business Plan: Using multiple email accounts in one account ID

I’m trying to contact our account manager of business subscription (Gina) but to no avail. I’m not sure if anyone here can help to answer the question.
Currently, we’ve one email address tied to our business subscription and we want to create a new email account and tie to the same account ID. Is it possible to share the ID for 2 email accounts? How can we use another email account in the same business subscription as app creator?

We encountered some errors while working on new app and the issue seems to lie in the excel files stored in office 365 OneDrive account where too many requests from different apps are trying to access at the same time. How to solve this issue?

Just share the app to as many emails and mark them as coauthor

Thanks.
Can we still publish the app in white label? Is the app require to be in the owner ID account in order to publish white label?

Yes, any app in any account can be published as white label. I assume as it is a business subscription, and not a public app ? (meaning it requires login).

If you want to publish a white label app that is public and requires no login, then you would need to host the app in a different Publisher Plus account ID.

Yup…we’re in business subscription. I understand that for business plan, 100 users are allowed to use the apps. Until now, we’ve never exceeded more than 10 users. However, there’s an app coming up where we will have more than 80 users. So, I just want to make sure my understand of 100 users is correct. As long as I share the app (add an email address) is consider 1 user. So, I have multiple apps and those email addresses added when I share the apps must not exceed 100 users. Is that right?

Yes, correct. You can always contact sales to get more licenses if you need more than 100.