Stranded wire comes in a variety of different # of strands (more strands = higher cost) for the same gauge wire. The greater the number of strands, the more flexible the wire. In addition, the insulation type will also affect wire flexibility. Use crimp connectors on ends that are placed on screw terminals. Aways twist the strands together, use proper wire strippers to avoid cutting any of the strands, and test your crimp connection by pulling on the wire/crimp connection to ensure a soild connection. If you can't get a small enough connector for the smaller gauges of wire, strip more insulation and double or triple back the bare wire into the connector before crimping.
Solid wire is highly prone to breaking where you strip the insulation, as it can be easily nicked, which will lead to failure if you don't use a wire stripper. Use small zip ties and Velcro wire ties to bundle your wiring paths as much as possible.
