Well one way to effectively tell how resistance and voltage are effecting your vapre is to use the
Ohm's Law Calculator.
You can input the resistance and your voltage and it will tell you at what power/wattage you are vaping at. When it comes to wattage think of it as a light bulb. A 100watt light bulb is brighter thana 75 watt light bulb. What that means to a vaper is that higher watts = more heat.
What this means for example is if you took two atomizers both identical in every way except one was 2ohm and the other 3ohm with the same juice in both, you could use the calculater to find the voltage it would take to get the same amount of watts out of both devices and have an identical vaping experience!
It is of course reccomended that you use SR(standard resistance) or HR (high resistance) devices to get the most use out of your variable voltage device. In my experience, you can use LR (low resistance) devices with your variable voltage mods just dont start off trying to vape at 6volts.
When I get a new atty/carto/etc I start on the low end and adjust up to get the flavor/TH that i prefer. Most times I am well within safe limits using LR devices because before I get to the point of it not being safe I find that my juice tastes horrible and burnt. Thats a good indication that A) your voltage is set way to high or B) it's probably past time to add more juice.
Right now I'm using a HH. 357 510 hybrid atty advertised at 2ohm (1.8ohm checked with the Provari) I like to use it set at 4.2 volts for almost all of the juices I currently own. Which pushes me close to about 10 watts (9.8watts to be exact). Using the calculator I can see that at this setting I'm pushing 2.3 amps (2.5amps being about the highest "safe point" depending on your device).
Point being, feel free to play with the voltage. Start low and work your way up and only go as high as necessary to get the vape experience that you want out of the gear you are using. Don't try to experiment and put that 1.5ohm device on and set your mod to 6v, especially if you don't have in built safety features such as the Provari, and expect bad things not to happen. Play it smart and you will be just fine experimenting with a wide range of devices at a wide range of voltages without having them blow up in your face.
Hope this helps you out a bit and...
Happy Vaping!!