PippalL, unless cost is the deciding factor, I might consider the Juul for quitting, honestly. It's got some of the highest nicotine out there (and it is nic salts as well) so it may get you over the hump. Once you have been vaping a while and ready for more adjustable setups then you can look at tapering down from higher nic. I'd really recommend the Juul for a closed system to just about anyone trying to get over the quitting hump honestly, unless they were smoking 3 cigarettes a day or something.
About the "weight" it may not be "weight" at all. Ecigs can dehydrate you which can often lead to higher water and other liquid consumption, plus your body is detoxing from all kinds of things and that takes a bit of time. By all means exercise if it helps you (it often IS helpful) but don't do it in a "OMG I am going to gain 50 lbs if I don't," kind of fashion. I gained 10 lbs quitting and switching to vaping, but I really had to work at it, even though I've had periods of illness where I haven't exercised (I generally do, as part of my normal routine). People still ingesting nicotine tend to not get the "quitter gain" that can be seen at other times. Those were 10 very needed pounds, but I still had to eat more to achieve it.... Weighing yourself daily ATM is just going to be one more thing to drive you nuts, if you do it. Weigh yourself in a month and continue healthy eating and (reasonable) exercise. I'd be shocked if you weren't fine.
The only exception to this that I know of is that sometimes thyroid issues show themselves (there is some weird thing about smoking, vs vaping, which can somehow "mask" thyroid issues. If you find yourself cold, less energetic, and sort of lethargic, you might want to get a thyroid check after about a month, to see if it's still functioning optimally. If it isn't, treatment is pretty easy and if it is, well, at least you know for sure that everything is doing well.
Best of luck,
Anna