Google Accounts

In admin interface of our corporate e-mail Google — a word about it. I doubt that Google would allow such integration would not include such an option there: after all, corporate e-mail to a specially created as a thing in itself, separate calendars, separate docks...

I have gugliotta tied to a personal domain. And I am registered in Google accounts(e.g. using YouTube) to this e-mail(login). It seems that any settings in admin.the panel on this point. However, I don't have a corporate subscription, and private free.

Free (don't know how in corporate) in the admin main account to register the services available to this domain.

I use 2 parallel apps account tied to your normal Google account. I don't understand what you are having problems. Each other they did not interfere.
When using OAuth is invited to choose which account to use.