Its not really as clean cut as that, and sure theres someone else that will explain it better. but there's 0.2 ohm coils that can handle more than 50w, and every coil could be compatible with your coolfire(if above the lowest resistance coil it will fire).
For example my rx200s I have updated so it will push out 250w, but could still run a 1.8 ohm coil at 10-15w.also it will only fire a coil above 0.1ohm so anything super sub ohm wont work at all. every coil/ tank/juice combination will have its own individual sweet spot, if the wicking is not right or the coil gets too hot it will get burnt.likewise if its flooding or not enough watts then not good vapour or flavour.
Equally you can have a 0.2 coil made of a small amount of wire or a large amount of wire, the latter handling more power than the other.
Dont feel u need to run ur mod at full power just cos u can, experience and gradual experimentation towards that will be far more advantageous in the long run, watch vids on you tube and alike, and understand what ur doing before jumping in the deep end.
Also take into consideration knowing what ur batteries can handle too, u dont want too exceed the amp draw limit on the set up your using, use good reputable batteries, learn about ohms law, be safe and vape on!!
Hope this helps