You asked about wire nuts and solder for your wiring connections and the answer to this requires that I make a statement about the wire itself. Please understand that it is decidedly not
my intention to find fault with the way anyone else has chosen to wire up his/her bus. My comments are based on my background as a marine electrician involved in wiring for harsh (and moving) environments. If you used something else in your bus don't flame me
; this is just my viewpoint.
In my opinion you should consider not
using solid copper wire for your AC system; for all marine applications stranded wire (and tinned in saltwater environs) is called for because it can withstand the constant motion and vibration of a moving vessel and solid copper tends to work harden and become brittle...and then break. It's also why all the 12-volt wiring in your car is stranded; that and the ease of routing stranded wire. Using stranded wire also makes it possible to crimp your connections (use a good double crimper); this is not only easier but has been found to hold up much better than soldered joints in moving vehicles and vessels. You might be interested to know that it's just about the only type of electrical connection made in aircraft and their needs are much more critical than ours.
A good solder joint is fine (except for vibration breaking it apart) but it's not necessisarily an easy thing to do without experience and it's very difficult to visually tell whether a solder joint has been done well or not.
It's certainly possible to do poor crimp connections but if you buy quality connectors (check out Terminal Town on-line) and use a good double crimper (the second crimp grabs the wire and provides strain relief) good results are easily obtained and quite repeatable.