While they may be a very close match, and depending on the screen you are using to view them on HomeDepot.com, we do recommend you reaching out to your nearest store. This way, you will be able to discuss your project's needs with a team member there and possibly look at display options. We hope this helps, and we appreciate you considering Hampton Bay cabinetry!
I think that's a combination of personal preference, and installation confidence factor. I've heard it both ways, but since mine are single-unit stand alones in a laundry, and I don't trust my walls to be parallel, perpendicular, or square or my ability to measure twice, I will be mounting my filler panels behind the lip! :-)
It will work with either base or wall cabinets just so the height of the cabinet is the same
My handyman was unable to attach filler panel because it never arrived.