I would say, get comfortable with building your own coils in RDAs before going any further. You don't realy need a bazilion of watts to produce huge clouds.
It's all(mostly) about the build.
There's no need to go to the super sub-ohm territory which you should't go anywhere near before you've done your homework.
Anyway for the regulated ones 100-150w is plenty enough. Vaping anywhere higher is nearly impossible due the warmth (some do but well... its not enjoyable)
So my tip would be to try read up on coil building and get comfortable with it, if you want the huge clouds. A prebuilt coil can only get you so far. Yet it won't beat a well made coil in an RDA. So i think you're looking in the wrong end here. More power isn't always the best.
EDIT: You don't need a mech mod to build the coils for an RDA they work just as good if not even better on a regulated (more consistent & safer for a beginner)
As long as you keep it within the battery safety limits (a regulated won't fire an unsafe coil for example, a mech would and **** can hit the fan)