Basically the 3.2 and up is ideal for all around. We have also a longer stroke 4mm. We will have 2.5 for 2.8 more or less for people that prefer shorter stroke down the line.
I personally use the 3.2 it's perfect to me for everything. Plus I like to hang my needle when lining. So the 4mm is too long for me.
When lining release the give a bit, tight it all the way in and release the adjustment know until you get some minimal give, that will give you stronger strike when lining than if you line with the stroke tight all the way.

For coloring I like to release a bit the give as well. For black and grey I recommend it tight almost no give. But again these are just suggestions. I'm sure you guys can come up with new formulas as well