Howdy, welcome to the ECF.
Mechanical mods are advanced devices, and require a bit of care and knowledge to operate. Mech mods have no safety features, meaning if you put in your battery backwards, you could be creating a pipe bomb. If your batteries are too low on voltage and you don't realize, you could be creating a pipe bomb. If you have a short in your coils because something metal is in contact with the actual coil, you could be creating a pipe bomb.. You get the picture, I don't recommend them to newer vapers.
Also important to note, with a mech mod your voltage is whatever voltage is in your battery. At full charge, this is 4.2V, and it goes down as the battery is used, but say the atomizer you're attaching performs better at 3V or 5V. You'll never be able to achieve that power.
You'd be much better off simply buying an RDA and using your current device, as it is most definitely capable of powering an RDA (variable wattage/voltage also means you can adjust the power to your coil, rather than adjusting the coil to your power), plus it has the added benefit of safety features. Getting into actually building is a whole 'nother beast, and can involve a whole lot of variables.
But I mean it's your choice, if you really want a mech mod you can go down that route. Just don't take me lightly when I say you really need to be educated. Even seasoned (self-proclaimed "professional") vapers have had lapses in judgement that end in catastrophic results.