Best to stick to patches.
After a quick deep dive on the topic, I found this: http://www.ncbi.nlm.nih.gov/pubmed/18852035 In short, cells from oral tissues experienced relatively more DNA damage. In absolute terms, it's not much, but reason enough to default to patches, versus oral routes, IMO.
Also, oral nicotine causes all kinds of gingival recession. This is pretty widely known (halfway decent source for this: http://www.ncbi.nlm.nih.gov/pubmed/2388141).
Duration of release? I believe you should leave it on 24/7. IIRC, it's not that nicotine improves sleep quality, but rather that nicotine withdrawal impairs sleep quality rather profoundly, and as such keeping the patch on at night allows for better sleep. I could be wrong here, though. Been a while since I've researched this.
(I am a non-smoker; have tried 2mg and 4mg gum, and find 4mg similar in some ways to having a 'bad trip'. (Light-headedness, freaking out, nausea, time-dilation.))
If I was a non-smoker though I would not start a nicotine habit at all. I wish I had never started smoking, it's a very difficult habit to reverse.
/r/electronic_cigarettes has a pretty good FAQ on these types of things, ignore their ridiculous $200 setups though, a bit overkill IMO.