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.
/r/electronic_cigarettes has a pretty good FAQ on these types of things, ignore their ridiculous $200 setups though, a bit overkill IMO.
(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.
Smoked for 18 years, snused for 2, and tobacco free for 2.
edit, for good measure:
http://scholar.google.com/scholar?hl=en&q=swedish+snus
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Oral use of Swedish moist snuff (snus) and risk for cancer of the mouth, lung, and pancreas in male construction workers: a retrospective cohort study http://www.thelancet.com/journals/lancet/article/PIIS0140-67...
Is Swedish snus associated with smoking initiation or smoking cessation? http://tobaccocontrol.bmj.com/content/14/6/422.short
Swedish Match Company, Swedish snus and public health: a harm reduction experiment in progress? http://tobaccocontrol.bmj.com/content/10/3/253.short
Steady-State Nicotine Plasma Levels Following Use of Four Different Types of Swedish Snus Compared with 2-Mg Nicorette Chewing Gum: A Crossover Study http://ntr.oxfordjournals.org/content/7/3/397.short
Should the Health Community Promote Smokeless Tobacco (Snus) as a Harm Reduction Measure? http://www.plosmedicine.org/article/info%3Adoi%2F10.1371%2Fj...
A long-term follow-up study on the natural course of snus-induced lesions among Swedish snus users http://onlinelibrary.wiley.com/doi/10.1002/ijc.21841/full
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Those were all on the first page of the search. Between snus and an imported unregulated mystery liquid that comes out of a bottle with a skull on it, or super expensive and annoying patches and gums, snus is really a gift to smokers.