Selling FBA AND FBM

Amazon prefers sellers use FBA, but also allows FBM. Since the preference is FBA:

i) would Amazon have an issue if I have a listing as FBA, but also have another separate listing for the same product as FBM, sold by the same account

ii) would Amazon have an issue if I have a listing as FBA and then add another listing UNDER that listing to sell as FBM (under Other sellers on Amazon)

Where can I find resources (rules and recommendations) similar to the above, so I can be better informed?