I've got the same question, I tried creating an api key with my own private google account but the drive I've been using so far is connected to a 'work' account with almost unlimited storage space. So far I can't access my previously created google drive of 8TB., I can create a new drive of 10GB in the account I've created the api-key in.
When I log in to my earlier created google drive with my work account I can still see the previously attached cloud-drive of 8TB, so it's still there and accessible.
With my work account I can't create a google project..