Everything that you are saying is the way to go. Generally speaking it is hard to add in wiring after the build is complete especially when the wiring is in the walls or ceiling. So design up front as much as possible. Try to envision how you will be camping and what you have to have to be comfortable. Also if you plan to sell your TD at some point, what you think others will generally want for features. One should not assume that everyone is a die hard camper who like to only camp in the boondocks and thinks creature comforts like insulation or AC power are for wimps. Not everyone is glam camp either. Too many extra features may not increase the value of your TD at re-sale.
Here is one wiring diagram: viewtopic.php?f=30&t=63874&p=1137763&hilit=wiring+diagram#p1137763
Search "wiring diagram" and ignore the trailer wiring about 7 pin/4 pin connectors.
Generally speaking the trailers are really considered 12VDC systems. Think a hardened tent/camp site. Teardrops are not motor homes. Most people assume that the majority of the trailer devices and appliances will be powered by DC. The DC system is drawn from one or more lead/AGM/Li batteries.
DC would provide power for:
* lighting ( cabin, galley, outside of trailer )
* DC outlets
* provide AC via inverters. [ Converting DC to AC has power loses. Generally is used for low power appliances ie charging a laptop. It can used for bigger power draw items ie a hair dryer (1500 watts) for short bits of time ]
For more elaborate builds, the DC system would provide power for:
* water pump
* refrigerator (yes, Virginia, there are DC frigs )
* water heater
* cabin heater
* outdoor lighting
* techie appliances eg computers, storage devices, phones, tablets
The DC system can be charged while it is being used. So you can continue to use the DC system while the system is recharging the batteries.
Charging the batteries can be done by:
AC connection : either shore power at camp site/home or generator
DC connections: from the towing vehicle (TV) (while moving or parked) or from solar panels (while moving or parked)
Generally speaking, one is charging using only one system at a time. Most TD have at least AC charging capabilities. Some people have all of them.
The size of your battery system will depend on your power consumption, duration of outings and access to charging systems. There are computations for this on the site.
AC is added to provide:
* charging battery via battery chargers/converters
* AC outlets: 1 or more
* Air conditioning
Again, the amount and number of connections will depend on how you are expecting to camp. Generally everyone adds AC at least to charge the batteries while at home. And even the most die hard boondock camper will occasionally stop at a "real" camp ground with power. Some people cannot live without their espresso maker and blender and 60 inch sound sound satellite TV system. They is stored in the chase vehicle or the second trailer.
There are various methods for installing AC wiring from just using power strips to power distribution boxes with built in charging systems. Look through the site, search on power strip or distribution box.
The two systems do not have any shared wiring except at the point where the battery chargers are connected to the battery. Similarly, generally the running lights, signals, brake lights, etc does not have any shared wiring with the DC and AC system.
Check this site for actual wiring diagrams. The most important thing is to have proper grounding and fuses for the various circuits.