Answer from Epson: "They both adjust the platen. Setting the paper thickness will adjust the platen accordingly to the papers thickness. Adjusting the platen directly will alter it accordingly, meaning narrow, standard, wide, or wider. Adjusting the paper thickness will adjust the platen gap accordingly to the thickness setting that you input. The issue is that a lot of times people don't know the specs of the paper and do not know that paper thickness settings to input. Adjusting the platen gap setting directly is more of a general setting. Paper thickness setting is more detailed. Software will overwrite hardware."