Leaders are a personal choice when pulling plugs. I dont use leaders with hot shots and other similar plugs. You dont worry about line twist if your plugs are tuned properly. The only swivel you need is #7 barrel swivel between the plug and a single siwash hook.
As for the right distance to let out your plugs, Thats all trial and error. 40' is a good starting point, Sometimes its longer other times its shorter.