Personally, I find that my KFL needs a touch higher resistance to get a similar vape to what I was getting on my cartotanks. I like 2 ohm cartos, but I coil my KFL's at 2.4-2.6 (I'm still tweaking a little bit - I've been from 1.4 to 2.9).
Different coils are going to affect it by surface area in contact with the wick, how fast they heat up, how the coils are spaced, etc. The microcoil thing is just the latest bandwagon - they aren't the endall/beall for your juice. Try em, if you like em, cool, if not, try something else. I went a touch bigger in ID (I started at 5/64, went down to 1/16... I'm happy with a 3/32 now). The advantage of a twisted coil is getting more surface area, being able to use a lighter gauge wire (which is more resistive) but dropping it's resistance to allow for more wraps.
It's possible to use too little cotton, but it'd be tough. All that's going to happen is you're going to burn off the juice at the coil & the wick's not going to be able to keep up. With a tiny amount of cotton, as long as it's fluffed up sufficiently, it shouldn't have too much of a problem keeping up. It's going to end with a similar result as using too much - not supplying the coil with juice (either it can't get there, or it's being choked off) & you're going to burn your wick. Keeping cotton fluffy helps both, either you see right away there's too much there or you provide enough negative space for the juice to flow through rapidly.