So I figured out that I can use a 3D sketch to drive reference plane dimensions. This works great if the parts referencing the planes are parts in the master assembly. I ran into some trouble when I had parts in sub-assemblies referencing the 3D sketch dimensions of the master assembly. My parts in the assembly would only update after several rebuilds, lesson learned. To correct this issue, I created global variables in my master assembly connected to the 3D sketch driving sketch and fed those variables down the sub-assembly parts. This works pretty well, but it does take a while for the rebuild to update.
I also wanted the hinges and latches to update their spacing and quantity with a change in height or width. I used a linear pattern for the hinge holes, latch holes, and their spacing. I then created global variables in the master assembly for "hinge/latch spacing" and "hinge/latch instances" and linked then to the linear pattern sketches in the parts. I created a few equations at the part levels that referenced the 3D driving sketch to evenly space everything at the height and width grew. I then used an IF statement in the equations to manipulate my "hinge/latch instances" after a critical spacing was reached. When I added the hardware to my hinge/latch holes, I used a feature driven my a pattern and the parts would update with everything else.
I hope this helps someone else as they learn more about SolidWorks! Feel free to ask me any questions if I'm not being clear!
Any design that I do I start with a part that I call "A Skeleton Sketch Part" - I have all my information in that part, which only consists of Planes and Sketches, however you could have basic 3D modeling if you would like. This Part is the first part in every sub-assembly and also in the main assembly and everything is built off of the sketches and planes that are in that Skeleton Part. There are many nice features that you can apply using this part, however the best thing that I like, is the ability to break down my sub-assemblies and work on them individually without having to have all my assemblies open, because all the information comes off of the same part. Then when you go to insert the sub assembly into the main or another sub assembly, it just snaps in place with no interference's.
Might take a little more thought or getting used to, but changes are so easy........