I started getting away from the details of it so much once I realized regulated vv/vw mods don't really rely on hard figures like a mech mod does. Maybe there's a better way to do it, my experience has been more trial and error. It seems others vape at higher wattages than I do but then many are vaping on dual coil builds while mine are single coil.
It may not be the same, I haven't used prebuilt coils since I stopped using clearomizer ego style vape stuff. I wrapped my coil and use it on an rta. It comes out to around .51 and I've been vaping various flavors at around 32w. Some flavors seem a little muted or if the vape doesn't feel warm I turn it up to 35w, other times it starts tasting a bit off. Not quite burnt but overcooked almost so I turn it down to around 30w.
Premade coils seem to come with a wattage range but I'm really not familiar with them. Not sure if it's a suggestion or more or less to give an idea so people don't grab a coil and try vaping it at 120w and burn the coils out. My method isn't very scientific at all, maybe others will have better info in regards to better settings. Instead I start off lower and if not getting much vapor or if the vape's too cool I turn it up a little but basically leave it up to taste. I tend not to worry so much because I'm not running anywhere close to 50w+ and it's a dual 18650 mod.
Just for the fun of it I went to steam-engine's website and factored in all the details, wire type, twist count, single coil, leg length etc. It said at around 50w I should be getting a 'warm' vape. Tasted almost immediately burnt.
http://www.steam-engine.org/
I'm more about taste than clouds and taste is subjective so hardly scientific. It could be my particular rta though, it doesn't have wide open airflow like some do. That could definitely affect my personal experience vs yours vaping on a different tank.
After a little checking around it seems some people are having issues with the crown II coils including the .5 ohm ones. Dry hits, coils burning out, burnt taste. Someone on another forum mentioned poking holes into the juice flow holes poking the wicking with a needle and how difficult it was. It sounds like they may have had an issue packing the cotton wicking in there too tight. That could cause a dry hit for sure if the wicking isn't keeping up. When it's saturated with juice it would probably vape fine, once taking a few vapes esp at higher wattages it could use up the juice in the wick and not be able to reabsorb more juice in time for the next hit. Others suggested trying thinner juice, higher vg juices wick a bit more slowly and may contribute to the problem.
Another person said they contacted uwell and found there may have been a printing error on the coil package. That the lowest wattage listed was actually supposed to be the highest wattage. They said for the .5 ohm coils that would be 50w max. Take it with a grain of salt though, just passing along info I came across from another user so no way to verify if that's true or not.
Here's a review with some folks having similar issues within the past 5-6mo in the comments section.
http://vaping360.com/uwell-crown-2-review/