I'm not sure anybody can help you with this - we each have our own version of "must haves" and our own idea of what needs to be readily available and what can be squirreled away is a remote space.
As you surmise, packing a Class B takes some extra forethought and it is quite likely you will have to do without some things you carried before. It will take a few trips to figure it out. The best thing would be a short trip before you attempt the 3-4 week one, to test out what works best for you.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC