I've only been vaping for about 6 days now, but within a day or two I began to see insomnia at night, followed by feeling dead tired all day (Hence me responding to this post at 3am my time when I have work at 8

).
But, for the most part I would say I am not getting much of a need to smoke a cigarette but I can certainly feel my body is in serious flux from time to time. I know occasionally I have been chain vaping 24mg and as an ultra light smoker it is just too much. If I settle down to 18 or 12 at night I seem to have less issues with rapid heart beat, floating feeling, overly harsh throat hits.
However, my body is certainly starting to feel the effects of being without those other toxins it relied on and no doubt it will be a bit of struggle for a bit here. I'm assuming it will pass, because aside from those non-frequent moments where I feel uneasy in my own skin...I've already been feeling much better.
Hope you get to that right level for yourself. Also, drink water! I thought I drank a lot of water before I started vaping and I've found that I need about another 3 or so glasses throughout my day now due to my new found love of vaping!