What I currently have:
- American Express
- Comenity - 2 store accounts
- Synchrony - 3 store accounts
- Citi (really DSNB) - owns 1 store account
- Capital One - owns 1 store account
That's not including another Synchrony store account and a Kay Jewelers card that were closed for inactivity.
What I actually use: American Express, Discover, and a Barclay's card in my wife's name (plus a couple of the Synchrony accounts infrequently)
To answer your other question it is possible they would grant you two accounts, even of the same product. However, if you didn't submit two separate applications, I think it's more likely that the second email was just an error/glitch on their part. Have you looked to make sure neither email referenced the last four digits of your account? As mentioned, you can certainly contact them to make sure, but I suspect just the one account was actually opened.