Am I allowed to create another account and play both on same device or will my main account get banned?
Am I allowed to create another account and play both on same device or will my main account get banned? Yes.
Also, you can have one account on multiple devices, but you can't play on the same account on different devices (there shouldn't be a reason you do that anyways). So you can be signed in on your phone and your iPad, but can't play on both at the same time.