So you want to quit smoking cigarettes but there are too many devices out there now that use different juice like salt nicotine(or salt nic for short) or freebase (more commonly known as premium or regular vape juice) so I'm gonna go ahead and clear up some of your concerns about these different juices.
First lets go over Salt nic juice, they by standard, have the same amount of nicotine found in an actual tobacco leaf or your average cigarette. Nicotine salts use benzoic acid, which then lowers the pH. This reduces the alkalinity, allowing vaping at lower temperatures. All this means is that the juice is a thinner base making it smooth in small amounts making it perfect for most pod system devices such as the novo 2 or the mini fit but due to the higher nicotine levels in these juices they will have harsher effect in a device that provides a larger hit. Pod systems are best hit more like an actual cigarette so you'll wanna hold the vape in your mouth first then to your lungs this is referred as mouth to lung. Most vape companies will provide salt nic juice in 30mil bottles which makes them more cost effective than your average disposable vape. Due to the higher nicotine concentration these juices tend to still keep you addicted to the nicotine just without the cigarette. Salt nic can still be a healthier alternative to smoking, but if you are looking to eventually quit smoking it can be more difficult with just staying on a salt nic device.
Next we will move on to freebase juices, Freebase is the more traditional form of e juice, with nicotine that is closer to its purest form. This allows the smoke, when going directly to the lungs, to be completely enjoyable, even in large amounts. The nicotine levels for freebase e juices come at 0mg, 3mg, 6mg, and 12 mg. These juices tend to come in bottle sizes like 50ml, 60ml, 100mil, and 120mil, which makes them the most cost effective of all vaping. Freebase juice is more commonly used on sub-ohm tanks instead of pod systems, though there are some new pod systems that can use freebase juice. With these you want to take the vapor from your device straight to your lungs in one hit, this is known as Direct to lung. Due to the lower level of nic these juices do make it more possible to get completely off nicotine and kick that cigarette habit for good.