It's a rebranded AER:PP, now that PP is worth pennies after the rename. Smart move, but worse for the profession.
No - it's the old "Short papers" section of the AER. That was a legit AER and not a PP. They are just trying to solve multiple problems in the publication process by spinning it out as AER:I (including endless revisions, excessively long papers, too much time/effort spent 'framing' as general interest, and need for more top outlets for publishing).
I hope it does well. Goal of the AEA is to have it perceived as AER > AER:I > AEJ's. Given that AEJ's have done incredibly well, this is not an unrealistic goal. Of course, they will prioritize HRM's in the beginning to start a positive citation cycle - but this will hopefully be less so over time.