So maintain a slight gap between coils - dont make a microcoil.
Personally i start getting warm vape at much higher wattages - beyond 70W or so normally. ( But at those wattages the nic concentration is also critical, to avoid discomfort. Normally when i vape north of 60W/70W, i go to 1.5mg )
But it all depends on air flow and the suction force. If i reduce the air flow, the vape will get hot even at 15W, its really easy to do. When one sucks with full force on an rda with good air flow, even a 60W vape will remain cool. Also, a little spacing between coils will allow you to go to higher wattages without a hot vape
Please try and see
And with the VS rdna 40 & vtc mini, you can try Ni200 builds on your rda to regulate the temp also