Thanks everyone for all the comments and guidance. I appreciate the patience while I figure this stuff out!

I think I get it - The problem is the switches on my cars have JST/BEC connectors and my battery packs have universal/Futaba J connectors. So like you all said I'm just going to cut off all the existing connectors and make everything Deans. Or I can convert the BEC plugs to Futaba J. I guess you just have to pick a connector type and go with it! That way no matter what I need to connect I can always have extra connectors on hand to solder on and make it fit!