If the device has built in variable voltage than it is not a true mech mod. The itaste i34 is a VV device, albeit a very beast one. As others have stated, Mech mods are nothing more than a battery tube. The main benefit will come if you intend on using RBA/RDA and plan to do sub ohm builds as most VV devices will only be able to push a limited amount of watts and therefor can't fire the low sub ohm coils. You can put a kick in your mech mod if you really want VV but it defeats the purpose and you won't be able to do sub ohm very well. Personally, once I went mech and started building my own coils i never touched my VV devices again. But then I like sub ohm coil builds. If you have no intention on doing sub ohm, and I don't recommend it unless you seriously do your homework, then a VV mod will work just fine. I am not a huge fan of the itaste i34 but that's just my opinion. It's just too big for my taste. If I was gonna go that big I would just get a Big Nasty or a Hades mech mod. If you plan to go mech, here is what you need to consider;
1. Voltage drop: better mech mods have little to no voltage drop. And yes, you will notice a one volt drop when you fire.
2. Switch: do you want spring or magnet.
3. Battery: High Drain IMR are preferred, especially for sub ohm. Sony VTC5 are some of the best but that's another debate.
4. Charger: get a good one. Nite Core or Efest intellicharger is your best bet.
5. RBA or RDA: This is honestly equally as important as the mod itself. Research the different styles, pros and cons, and get a good one. Kayfun is best bet for a newbie. They are basically bullet proof.
Hope this helps.