I can't really speak to the premade factory coils and their 'ranges' they list. Some folks have said they've been in contact with uwell and the wattage ranges for crown II coils are printed wrong. The 'min' wattage listed is actually the max recommended, at least for the .5 ohm coils. All three of those are dual coil heads, the .25 uwell and .3 eleaf ec are ss316, the .8 uwell is kanthal A1.
A 0.8 ohm coil is higher resistance than a 0.3 and the same wattage would be pretty harsh on it. As resistance drops it takes more wattage to power it. 12w on a 1.5ohm coil would have it cherry red in a heart beat, 12w on a .38 ohm coil won't hardly do squat. It makes sense the general wattage range for the higher resistance .8 would be lower than .25 to .3 but can't say for the difference between the .3 and .25.
I think they're just trying to give a ballpark range for people who are unsure so they don't say 'well I used 10w on my coil and no vapor' or 'I hit this with 100w and now it tastes burnt'. It may also have to do with the type of coil, coil material etc. Part of it is the resistance of the coil, ss 316L has a lower resistance than kanthal A1 so 26g ss316 in the same coil id and # of wraps would have a resistance more similar to the same build with 22g or 24g kanthal.
At the same time comparing 2 identical coils, being thinner there's less wire mass on a ss316 coil than a lower gauge kanthal. Both may read .5 ohms but with more mass the kanthal may take more power to heat it up to make up for slower ramp up time.
Someone else may be able to explain it better and there may be better info regarding factory coils. If it were me I think I'd start somewhere around the min and just slowly work my way up until the vape was how I liked it in terms of flavor, heat etc. I wouldn't focus too heavily on what they claim is the 'proper use range'. Meaning they might say the ec coil is good up to 80w, if it starts tasting burnt or cruddy to me at 55w or 60w then their suggestion no longer applies.
Part of it will be subjective. If I hand you a canned beverage it's up to you how to drink it. Room temp, chilled, over ice in a glass, out of the can, with a straw, sip on it for an hour or chug it in 2min. I can't really tell you how you like to consume it best. What's enjoyable for one person may not be for another.
