Regarding the difference, I echo what everyone else has stated. There are tons of options out there, and I have two regulated mods, a VaporShark rDNA 40 and a Sigelei 150; both are excellent devices, with the rDNA having temp protection with Nickel wire, of course. I use the Sigelei 150 as my go to mod, I just like the extra power, although I rarely go above 75-80 watts. Two batteries help with all day vaping as well.
I also have a mechanical, a small SMPL mod, but it rarely use it. Good luck, there's a lot of choices these days!