I've built a half dozen boxes, and I built my first wall over the last month or three. I can tell you what I learned, even if it isn't any advanced knowledge.
You will want (I say NEED) the kreg jig. An invaluable tool for this type of construction, especially if like me you are cutting your panels outside of the car then building them together inside the car. Rabbet joints are a great idea for stability, I didn't do it for all my corners because I'm lazy.
2x4's as a shell is definitely overkill, but that's not always a bad thing if you have the airspace to spare. I opted to double layer birch plywood, which afforded a lot more airspace than I needed, so I used 2x4's for some serious interior bracing. Give yourself a few extra inches than you need in front of the wall for seat/subwoofer clearance. Triple baffle if possible, double would be fine with a lot of bracing.
Look into PL premium adhesive. I liked it better than Titebond for some parts, as it isn't runny and is easier to get exactly where you want it to go, as it is used in a caulk gun.
Measure everything a bajillion times, take into account the lowest point of the roof, the narrowest portion between the sides, and the highest point of the floor. It will be much easier to build a flat panel that fits between the narrowest points than trying to build complicated angles around them. Consider fiberglassing over the wheel wells if your wall will be built over them, it's easier than cutting squares or kerfs to to build around the wells and saves you some airspace.
Leave extra space for amps and batteries, this is where I shot myself in the foot and just today figured out the optimal way to fit everything after wrestling with a few hundred pounds of batteries all weekend. If I had left just 4-6" extra clearance for the batts, it would have been easy peasy going in and I probably would have still had enough air.
Port down the middle if it's a daily or demo machine. Build the port as big as possible.
Read over every build log you can find, plan to spend more than you thought you would, don't be surprised if you get stuck and have to spend some time thinking on a problem or changing your plan. Have fun and take pictures to help others. I will be posting some pics when I get them all together.