To the original poster. Look back to Ohm's law and see what you can change to get the power (watts) you want.
You can change the resistance (Ohms) up = less power down = more power. In a mechanical mod this is all you can change, but you can change it a lot. At .5 Ohm with a fairly fresh battery you are getting about 32 watts. A mechanical mod with good
batteries will do this with no problem. A
dna 30 will not.
You can change the voltage. up = more power down = less power. In VV/VW you can change this. 5 volts with a 1 Ohm coil will give 25 watts. Your DNA 30 will do it but the DNA20 falls a little short.
The VW part of a VV/VW comes from the computer. The mod measures the resistance and varies the voltage to achieve the desired wattage. If you have a 1.2 Ohm coil and ask for 18 watts you will get 4.65 volts.
How do you want to vape? If you want really high power it is mechanical with low resistance coil. Otherwise it is up to you. Either will work but the VV/VW is a lot easier. With a mechanical you need to be spot on with the coil build .1 Ohm is a large difference but a VV/VW will be just fine with it and change voltage with the press of a button or even change on it's own in VW mode.
A little bit about safety. There is a limit to how much power a battery can produce. Exceed it and the battery will be destroyed along with an unlikely explosion or probable hot gas. a VV/VW mod has a bunch of safety checks built it. Most will not let you put the
batteries in backwards, drain them so far it hurts them, overheat them, etc. Generally a smart friend looking out for you. A mechanical mod will let you do whatever you want, push the button and have at it. Generally the dumb friend who will let you eat that inferno pepper.