Yes, KangerTech makes a wide range of coils for the Subtank/Toptank line, including those you mentioned.
Your particular battery either operates at a constant voltage somewhere around 3.7-4V or else will start around 4.2volts fully charged and slowly drain as you use it (I'm just not sure which it is with the Subvod batt). Because you have no way to change the voltage or wattage, changing the resistance of your atomizer/heating element/coil head in this case is the only way you can fine-tune your experience to a certain degree.
On a battery that is unregulated or gives off constant voltage-- yours is one or the other-- lower resistances will achieve the following: a warmer vape, larger clouds, increased nicotine delivery through sheer volume of vapor and quite possibly increased absorption, decreased battery life, increased stress placed on the battery (but entirely safe in this case).
Higher resistances do... basically the opposite, in terms of "side effects," as it were. Your battery will last longer, it will be a slightly less "rowdy" vape, a cooler vape, and not as much vapor output. As you noted, you can use higher nicotine in this case.
Because your battery puts out no more than 4.2 volts, and possibly less, most people wouldn't find that 1.5ohm very satisfying. It is very common to run a 1.5ohm coil closer to 5V (+/-) on regulated devices, which your battery simply can't do. The 1.2 is a definite possibility, and you could increase your nicotine for certain. I don't know what levels your local store sells, but as much as you can afford you are better off going up slowly in order to find your sweetspot rather than jumping straight back to that 15mg.
Here's the thing: I know we can't all afford to buy everything we want whenever we want it. But as much as possible, the best thing you can do is to fiddle around some to zero in on what you like. If you get bit by the vaping bug, this might be the first of many devices. If you continue to just want to not smoke, then you're just as well taking them time to figure out what makes this battery work for YOU. I can talk at you until I'm blue in the face, and basically have, but in the end my advice may not be right for your style.
That all said, the subvod kit looks like a nice, simple, straightforward piece for beginners. I would continue to see if you like the 0.5ohm coil heads with 6mg nicotine juice or so and you can certainly try the 1.2ohm heads with a higher nicotine juice (say 10-12mg, but this is a guesstimate). There are .5ohm coil heads in both regular kanthal or maybe stainless, and also claptoned kanthal. If you don't know what that is, it's fine, all I'm pointing out is that there are at least four different coil heads you can try on your device. There's absolutely no reason you can't try the 1.5ohm coil heads either, just know that on that battery it might be a weak vape.
DO NOT attempt to use Kanger's 0.15ohm Ni200 (nickel) Subtank/Toptank heads on your device. These are meant for temperature control, which your device definitely doesn't do.
I realize this is a lot to take in so feel free to PM me if there's anything you need beyond this thread or if I can make myself more clear.
