I got the ESI kit.  Directions kinda suck. I have a 23 limited w/ ram boxes and factory tri fold.
Is it water proof? No.  With the ESI kit…rain stays out 95% or better.  But going through a touchless car wash OR using a power washer, it’s going to get a little wet in there.
Best thing you can do is crawl into the bed and have someone shut it…look for daylight and see where you can add sealing.
If I expect heavy rain… or don’t want something to get wet, I either stuff it into the Rambox, back of the cab…or wait…