NOTE: I'm not a doctor. You may want to speak with one if you're looking for sound medical advice. There are some on this board, and you may want to reach out to them.
That said, I'm going to say something that may not sit right with people who advocate quitting smoking. Inhaled tobacco smoke DOES contain psychotropic drugs that are beneficial to people who suffer from depression and a wide range of mental ailments. Some are not replicated by the pharmaceutical industry, so you can't get them anywhere else.
I get this information from here:
NIDA NOTES - Tobacco Smoke May Contain a Psychoactive Ingredient Other Than Nicotine
I have a friend who's been watching me merrily vaping away, yet isn't inclined to switch from analogs. He's a very self-aware individual who suffers from depression, and smoking gives him the needed chemicals that work better than any anti-depressant he's ever tried (and he's tried a lot of them).
Here's some information on MAOIs:
Monoamine oxidase inhibitor - Wikipedia, the free encyclopedia
My friend's conclusion was that it would be better to cut back his smoking to a level that is less harmful to his general health, yet provides him with the MAOIs that he needs, and I fully support that. Everyone gets something different from smoking, and vaping too, for that matter. While I agree that vaping reduces harm, it isn't worth a person's mental health. As it turns out, I didn't smoke because I needed the MAOIs - I needed the nicotine. But we're all individuals, so you need to look within and figure out what exactly you need. Maybe a hybrid solution would suit you best.
And you need to be peaceful with yourself about it. It isn't a pass-or-fail proposition. I use myself as a lab rat for life-change experiments and vaping's been one of them, but I always check myself when I see a negative impact. I'm not going to wreck my well-being for anything, no matter how loudly others may tout its benefits. As much as I enjoy vaping, if I ever feel a bout of depression coming on, I'll have a cigarette, no questions asked.
Any reduction in smoking is harm reduction. My friend has gone from almost a pack a day (from smoking with ME, because I'm a bad influence), to about 14 a day, and he seems comfy.
If you're looking to reduce the amount of smoking you've been doing, then maybe you should find your minimum on cigarettes and vape the rest of the time for nicotine. I don't know anything about WTAs, so I'm sorry, I can't give you any input on them.
My conclusion is: find your happy place, not someone else's.