I have a cap on my bed and bulit a platform for the back of my truck for a trip we took.
I can fit 4 19gallon husky storage containers under the platform and still have a foot of bed under the platform for storage. I have a few of those containers loaded and labeled with gear ready to go and swap them out based on activities.
Whenever I have anything in the bed under the platform with the cap closed the bed looks empty through the windows.
The platform is completely removable and takes about a minute and can be stored in the front of the bed stacked for full bad use
I would have a decked system they are great for truck camping