best way to make connections

I solder all crimp connections just to be safe. You don't have to if you have a top-notch crimper, but those cost >$300 and I don't have one. The "56 terminals" used throughout our cars are simple and inexpensive, but not as good as Weatherpack or Metri-pak. Most term them "spade terminals". You can also use the round "bullet connectors, especially for single wires like an AC compressor. Whichever you use, best to fill the terminals with silicone di-electric grease.