New to fishing and a few questions

[summers]

I like the idea of running a fluorocarbon leader not fluorocarbon line as a leader but a true leader, should I run a 6lb or higher leader line to the 4lb braided line. I know that line diameter is the true measure of the line size, but I see that most leaders are 6lb or higher. Or should i just use regular fluorocarbon line apposed to the true leader line? Also what lenght are most people using for a leader.
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