Nothing like asking just a small question about a subject like electrical systems
Part of the reason everything isn't together is because it would be a doggone book! Been done before
. I've been putting together electrical systems on boats for over 30 years now so a lot of what I say is based on that and the experience of trying to keep systems going in harsh environments.
YOU have to make the decision up front about what you're willing to put into a system; not only from a work standpoint but also from a monetary one. You can do it relatively cheaply with typical household type wire and fittings or you can develop a long-term, high efficiency system from higher quality marine type components. I am not here to tell you one is necessarily better that the other; just that they're quite different and you have to be the judge of what suits your needs. A long-term live-aboard bus would suggest different systems than a weekender/party/camping bus.
The primary consideration for your electrical system is that it's just that...a system. Every component in the system needs to balance with every other component in the system. No sense in having hundreds of amp-hours worth of batteries if you have no way to reasonably charge them. Where we usually start this whole process on a boat is to figure out what the energy requirements are...that is, what do you need on a daily basis to sustain your particular lifestyle. How many lights for how long, how much refrigeration, how about TV, stereo, video games, heat, air conditioning, coffee maker, microwave, computer, appliances, etc. If you don't know how much you're going to use it's pretty hard to figure out how much you need to supply.
I can tell you the secret to the best possible system is conservation; that is, using the least amount of electricity to start with. If you don't use it, you don't need to supply it. So high efficiency lighting can help; halogen and LEDs takes far less power than incandescent. Choose things like high efficiency refrigerators, low power fans, etc. Make every effort you can to reduce your need for electricity and the job of supplying (and replenishing it) gets much easier.
Make some early decisions about your big energy users; heating, hot water, cooking, and air conditioning. What's going to be electric, what's going to use propane, etc.
A lot of these decision will (or should) come from the type of use you'll give your rig. You want to live off-grid as much as possible but will you be close to other people; is running the generator going to bother them? What's going to be the easiest fuel to obtain; or the hardest? You can have a whomping big propane tank under the bus to supply the refrigerator, water heater, furnace and stove but when it runs low are you willing to drive the bus to somewhere to get the tank refilled (that's a major bummer if you're setup in some beautiful location). Maybe four refillable tanks in a compartment (like BruinGilda; on this site) is a better deal so the bus doesn't have to go to where the propane is. Maybe cranking up the big genset for running an electric stove is the easiest, best and cheapest method to cook. It's not inexpensive to get a really great electrical system setup with solar panels, wind generators, regulators, switches, monitors, high quality batteries and such. But maybe you hate the sound of that generator running and it's not an option except as a necessary evil.
Setting up a good 12-volt system to serve most of your needs is pretty straight forward. Ideally large, high efficiency cables (wire) will feed a central distribution panel that incorporates switches and circuit breakers (or fuses) for each of the circuits you need. DO NOT UNDERSIZE your wire; it's the single most ridiculous place to save money there is. Not only are the voltage drops (and therefor the efficiency) horrid but you create a lot of heat (wasted energy) and can potentially fry things (start fires).
There are some things that just don't translate to 12-volt use very well; like a microwave or coffee maker. Remember, for the sake of quick calculations you can figure a 12-volt gadget takes just about 10-times more amperage to run that does an AC gadget. The wire couldn't care less if the electricty if AC or DC; you can imagine then that carrying 10-times more current really takes much larger wire! Watts is watts; it doesn't make any difference whether it's AC or DC power. A 60-watt light bulb will consume the same about of power from either source. And watts is voltage times amperage. So a 60-watt light bulb running on 120-volts needs .5 amps; on a 12-volt system that same bulb needs 5 amps (there's that 10x factor). You can do the math on a 600-watt coffee maker...50 amps on a 12-volt system...that's some big draw!
Every conversion of energy loses something in the translation; so gas to electric, ac to dc, dc to ac all lose some efficiency. Knowing how to get the most efficient use of your energy is the key; and also the hardest thing to figure out. In the winter it's likely that a good water-cooled generator is the most efficient use of fuel if you also send hot water from the running generator to high effciency radiant heaters (like Heatercraft units). You're getting AC, DC and heat all from very little fuel. And while you might balk at the cost of fuel to do that if you figure the investment (and maintenance and replacement costs) of systems that do that in a different way you might be surprised at the outcome. Most of us don't want to listen to a generator that much so we seek other options like batteries. They're really inefficient, so much so that if we're relying solely on fossil fuel to replenish them you'd be money ahead burning the fuel to produce the energy directly. That's where wind and solar energy comes in; hopefully we'll capture some energy that way and not have to depend solely on fossil fuel. There a caveat here; in the boat world there's a saying that "the wind is free; catching it is not". In other words, those sails ain't cheap. So while catching the wind and harnessing the sun for our electrical system is 'free'; the equipment to do so is anything but. It's all a matter of balance.
If I were going to the trouble of putting together an 'all-round' system that incorporated power generation (from fossil fuel), wind generated power and solar generated power I would certainly build the 'best' (in terms of component quality) system I possibly could with high efficiency and low losses. This is using the 'good stuff' and it isn't going to be had in Lowes or Home Depot or Ace Hardware and it isn't going to be cheap.
You can certainly do it any number of ways and countless folks have put together a make-do system that does; it's your money and you get to spend it the way you want to. That's part of what makes it so hard to write about the 'correct' or 'best' electrical system; it can be different for everyone depending on what your priorities (and financail resources) are.
Anyway, I can give you some input on 'how' to implement your systems but you'll have to decide first 'what' systems you want and how big (or small) they need to be.
Here's some food for thought; if you have enough propane (that would be by your definition of how often you're willing to refill) you don't need electricity at all (except the starting batteries for the bus and the genset)...until you add something like a TV, a stereo, a computer, etc. I've seen some great propane lights so electricity is needed for those. So just how much stuff do you have to run (or do you need) that will force you to install the wind and solar systems? [This isn't a challenge; it's just for provoking thought about what we really need.]
This is getting way too long; I've got to stop here.