No. of Outs when counting them is most applicable???

I understand the concept of counting your outs to the best hand.

But, what number of outs (approx.) is this useful for?

I have read somewhere that you are really only needing to do this when you have a weak draw: 2-6 Outs?

Is this correct?

I'm asking becuase I am trying to learn a table of Outs V %'s. I want to start with a range of Outs that will be most useful.

Thanks,
Ian