As far as sampling juices, the old 306 and 510 dripping atomizers are still around, but more efficient and effective are rebuildable dripping atomizers (RDAs) you build the coils yourself, which needs a knowledge of Ohms Law to do safely, though there are some places you can buy pre-wrapped coils to install into an RDA without needing to wrap them yourself, after that you just need some basic tools, wire snips, tweezers (preferably ceramic tipped), pair of scissors, and some cotton wicking like organic cotton balls, or "Cotton Bacon" "Cotton Bacon Bits" pre-sterilized unbleached/non-peroxide treated cotton, to install and wick the coils. Unlike the silica wicking most cartomizers/cartridges used back in the day, cotton transfers flavor way better, though I has a lower burning temperature than silica does so you have to watch how dry the wicking gets when using cotton and other such wicking materials, most pre-made coil cartridges in production nowadays (replaceable coils) use cotton as well, don't let the tank get to low on juice or you get a very bad scorched hit, 10x worse than a dry silica hit from back in the day. The term "Sub-Ohm" is any coil or multi-coil setup that has an Ohm Rating below 1.0ohms, back in the day Low Resistance coils were lowest 1.5ohms, and high resistance was in the 2.8 to 3.0ohm range, you now have "Standard Sub-Ohm" (0.5 to 0.9ohm), and "Super Sub-Ohm" (0.1ohm up to 0.49ohm) to contend and confuse you further. Sub-Ohm does require more power, direct relation to the diameter of the wires used (thicker gauges of wires like 22 and 24awg wires) compared to the older devices you remember used very thin wires like 30, 32, 34awg wire which needs far less power than a thicker 22awg wire, compounded further with very low resistance coils out there right now in the 0.1 to 0.15ohm range due to amount of wire in them needs 100+ watts to function right, where the older cartomizers and such from back in the day needed 5-8watts max to function properly.
Carcinogens/Formaldehydes/diacetyls and other by-products, yes, if you are to hot and reaching scorching wicking temperatures on the wicking, juice, wire materials, yes you are going to produce these chemicals, especially the drier the wick is, the worse it gets. If you don't go to crazy on the watts you output, the risk decreases drastically.
There are really two types of vaping these days
Mouth to Lung (MTL/M2L) which is low wattage, tight, restricted devices that simulate the draw of a cigarette or off a straw
Direct to Lung (DTL/D2L) which sub-ohm, higher wattage, loose airflow, devices that simulate the draw off a *ahem* water pipe chamber you have to clear.
For the most part, the mod (power device) itself plays a factor in type of devices you attach to it, it is the attachment that limits your ending wattage output and you have to juggle what you are wanting, relax back and sip at juice and still enjoy flavor and such MTL device like the Kanger Protank 2, the mod can accomodate the tank readily as it can accomodate a higher power D2L storm clouding tank like the SMOK TFV8 Cloud Beast, you'll have to decide what attachment type you will want, RDA mentioned above you can build these to what ever your style is low powered single coil just for testing, or super high powered huricane making cloud champ, which can be used for sampling equally well.
If you are looking to get back in and get a starter setup that will work quite a bit better than that Old Ego-C you remember, the Tarot Mod will be flexible
MTL Tarot Setup - The Tarot Mod with an Aspire Nautilus/Nautilus Mini/(Newer) Nautilus 2 in the 8 to 15watts range will be a beauty and very low maintenance setup, with coil head replacement for the Nautilus line being in the range of every 3 days to every 2 weeks depending on juice, wattage, and frequency you vape
D2L Tarot Setup - The Tarot Mod with say an Aspire Triton/Triton 2/Kanger Subtank (Toptank) in the 20 to 30watts range would need a little more upkeep (will use more juice due to the wattage is higher and vapes more juice) with a coil life replacement of 3days to 1 week depending again on juice, wattage, and frequency you vape.
