I have a 14ft. with no slides for the two of us.
I utilize the overhead storage. Clothes/shoes in duffel bags or plastic storage bags go over the cabinets over the bed. Miscellaneous items go into bins and then into the cabinets over the sofa. Plates and cutlery over the kitchen counter.
I have two shelves stacked on the counter with bins for food items. Under the sink are the pots and pans. Drinking water bottles go under the dinette-as-bed. The bathroom has a spring loaded rod with small shelves for soap, makeup, hairbrushes, and shampoo etc. The wardrobe has the TV trays, jackets, and outdoor stuff like awning lights.
Outdoor chairs, kick scooters, extra towels, oxygen bottles, fishing equipment etc. ride in the trailer and then gets stored while camping in a pop up instant tent.