I've had this come up a lot, and drawing from my experience I'd like to clear up some misconceptions.
You don't actually need big power or a mechanical mod to get big vapor from your RDA, you can do pretty well for yourself with 80 to 120 watts. It all has to do with understanding ohms law, and knowing the limitations of your device. Before you click way because ugh he's talking about math again, hear me out, this might change the way you use your RDA.
I believe I mentioned this in a previous post explaining ohms law; that if the power you're providing to your coils doesn't change, and the resistance of the coil increases, more voltage is run through the coils, which in turn increases the heat emitting from said coils (which makes more vapor). It's pretty simple, and with modern regulated devices this is pretty easy to achieve, as unlike their unregulated mechanical mod counterparts, you cannot increase the voltage sent to the coils, they are at a fixed rate (that of the battery itself).
To elaborate on that, let's say you only have 100 watts out of a two battery device in series. If you have a 0.15ohm coil in your RDA and you fire it up at the full 100 watts, you get ~3.9 Volts and ~25 Amps. Which would be a decent vape but nothing too crazy. Now if you used the same 100 watts at 0.5ohms, you would be running 7 Volts and ~14 Amps. That 7 volts is where the high resistance heat comes from, because voltage is talking about the force of electricity travelling through the wire, where Current is the amount. So there may be less going through the coils overall, but it's be backed by way more punch. Like if you threw a bowling ball, it wouldn't go as far as throwing a baseball.
There are some limitations to this however, the big one is device capability. A single battery device won't have the capability of putting our more than 4.2 volts, and even if it could it wouldn't be for very long. However a dual battery device in series can, as series means that it doubles the voltage output capability. So if you have a double battery device that can put out 100-150 watts, you don't need to invest so much in more power, as you do making your coils a higher resistance.
Another limitation is the coils themselves, so to achieve a higher resistance you need to do one of two things: use thinner gauge wire (as the thinner the wire the higher the resistance) or add more 'wraps' to the coils. The other option is make or buy multi-wire coils like claptons or alien claptons. Because they use thicker wire wrapped with a lot of smaller wire, it actually ends up being a higher resistance than a standard wrapped coil. Personally I've been using pre-made Alien Claptons with an extra wrap on them, and they come out to about 0.25 - 0.3 ohms in a pair.
I've found that using more complex wire designs actually increases the effectiveness of a higher resistance-lower wattage vape, because there is a lot of surface area on the coil the heat produced is much greater, and the flavor is better. They just take longer to ramp up to full power.
So the big question is why would you want to use a higher resistance coil combined with lower wattage? Everyone knows that low resistance and high power is effective at a warm and heavy vapor producing vape, so why change that method? Well, the big one is cost effectiveness. If you aren't looking to upgrade or spend money on a device with 150+ watts, but want to produce more vapor and get a more 'hot' vape, you can use this strategy to achieve this by working with what you have. As well, this actually can help increase battery life. By not using maximum amperage all the time (like you would with a low resistance coil and high wattage) you can drastically increase the daily lifetime of your batteries. Another thing (and maybe this is just me) but it makes more sense to build higher on a regulated device, it's honestly kind of the whole point of them existing, because by definition they do what an unregulated device can't: Regulate power.
To put it in a real world example, I use an RDA on a DNA75c Therion device, which only has one battery. And at 0.3ohms and 60 watts it performs like a mechanical would at 0.1ohms (in my opinion). I came from mechanical mods, and I always sought after more heat and more vapor, so when I bought a 150 watt device and used the same ultra low resistance coil and RDA, I was disappointed that it wasn't any better than my mech. That's because, like I mentioned it isn't meant to provide more power, but utilize it.
To conclude, if you only have so much power to play with, it's totally possible to get more performance out of your device and RDA, you just have to not try as hard.