First thing to consider, imo, is whether you want to make vaping a hobby or strictly a great way to be off burning tobacco.
If just a replacement, then what you're looking for is ease of use and reliability. Along with a great vape, of course!
The Provari gets consistently good reviews for reliability, and is on the high end for cost.
Units like the Vamo, Zmax, Tesla and others are towards the other end. (As is the SVD, but there have been reported problems with it's fire button. Mine's 8 months old and works fine, tho...)
For either end of the replaceable battery mods you also need at least two batteries and a charger (or two, for backup), adding to the up front cost.
But you get significantly longer vape time going this way.
I'd suggest sticking with regulated mods for now. If you decide later on to turn it into a hobby, a mechanical might be in order. Learning how to control your vape by way of VV or VW, before attempting a mech makes sense, so you know clearly what to strive for in building coils - the only way to control the vape with a straight mechanical.
For toppers, any of the glass bottom coils will give you a good vape. Replacment coils are inexpensive and easy to change. Some reading on how to clean and dry burn the single coil units will extend their life quite a bit. Duals, afaik, are not good candidates for dry burning, and may or may not be able to be recoiled like the singles. Glass tanks are impervious to any juice you put in them, where the poly tanks can be destroyed by some flavors.
Personally, I run an SVD, a Kmax, a Tesla and a Vamo V5, along with a couple of mechs (kicked). All but the Kmax are multi-button controls, which I prefer. (Not better or worse, just prefer that interface.) And of course a plenitude of Spinners and other VV ego styles from 800 mAh to 1300. (With those, I like the Kanger T3S, and the mini PT and Davides.)
I still like the original Protank, the PT2, the Davide Glassomizers, all single bottom coil, and all can use the same coil - which I do rebuild. And the Kayfun is a great rebuildable, have a couple (so far!

), along with a Squape. Not terribly impressed with the Squape, although newer models may have air flow control, mine doesn't.