Because of the load limits that are inherent in the 14 inch Marathons very little goes in the TM that is not light. All tools and extra equipment go in the TV. Clothes, linens, dishes, small television, small battery powered vacuum, small fan or heater depending on the weather, none-perishables, etc…( but all very light in weight ) go in the TM. The back battery storage area has extra power cords and hoses. The back bumper holds a few odds and ends. But nothing of any weight goes in the TM. I too came up from a pop-up, a Coleman Santa Fe. It had no outside storage to speak of so my transaction was not bad. If your pop-up had one of those external storage areas I can see where the adjustment may have you scratching your head for a second or two.
But then again, your pop-up experience will serve you well with the TM. Good luck and happy camping.