I'm looking to run the remind category. "No boosts other than AP boosts and food boosts are allowed" does this mean the save you load from hasn't used any strength/magic/defense boosts? is that to prevent people from maxing out stats for the DLC? To be clear, in order to run this category, do I need to go back and make a save file using no boosts?

That's exactly what it means. The game allows using up to 100 boost items so we don't want that to be the expectation.

You can make a save file quickly by starting with EZ codes, just disable them for the run