What is the difference between this and doing preferred and common? Curious to hear what you come up with.

Is the series A an equity instrument with debt features? If so, then I would look at how the payout is structured and controlled. Series B sounds more straight-forward. I would look at voting rights and liquidation preference. I don't believe equity with accrued interest is a common practice....that series A sounds more like a note with equity-linked features like a warrant.