How many total amps will your lights be drawing on each circuit? You cannot determine the proper size wire gauge without knowing this.
Avoid using butt connectors because there can be a voltage drop across them and they also have the potential of pulling apart. Terminal blocks with ring connectors are fine to use. Avoid spade terminals because they can pull out.
I don't understand why this is being made so complex? Do you have a spare breaker on your DC panel? You don't need butt connectors or terminal blocks if you do. Keeping your electrical system
simple means there are fewer links in the chain that have the potential of breaking.
If you answer my questions then I can better help you..such as if your lights each have individual switches and if you have a spare breaker on your DC panel. If for whatever reason you don't want to answer my questions then there is no way I can help you.