I have not ready the whole thread. All ecigs can use
eliquid. The
eliquid either goes in a cartridges that attaches to an atomizer (least popular way to vape) or in disposable cartomizers (combined cart and fresh atomizer inside each - most people can get a week or more use out of each) or some people use manual bateries that are sealed on the end with an atomizer and drip tip and constantly drip juice onto the atomizer (not good for when driving etc)
Rebranders (the seedy upper crust of name ecig vandors - the ones that don't offer blank cart/cartos or juice) may sell their ecigs with crippled carts (no silicone plugs, no indication of how to add juice) or crippled cartos (hard or glued on ends so tricks are required to fill them) and these same rebranders may say you void your warranty if you refill stuff. Most also only sell automatic batteries which are the batteries most likely to be damaged or killed by juice leaks.
If you buy any popular decently sealed manual model somewhere that also sells blank cartomizers for it, then you have a good system resistant to damage that you can use cartomizers you fill yourself. That can be a small (and w/ a short a battery charge since small = short battery charge) like a manual Joye 510 used with Boge standard reisstance cartomizers (slim ecigs can only use standard resistance, not the hotter LR cartomizers), to a hotter model like vapor4Life manual or Smokeless Image Volt manual (the small size has the shorter battery life, I recommend the standard or 78mm size for a 120mm ecig). Or if you want more battery life and the ability to use the hotter LR cartomizers, look at fat battery models Joye Ego or Riva 510 (Liberty-Flights.com has the new hotter Riva 510 kits and press 20% off upper left front page first to see the lowered prices). Or you can step up to mods of all shapes, 3.7v and variable voltage (mods have removable industrial type batteries and you buy the batteries and their charger separately).
As you shop - 100mah is about 1 hour of moderate
vaping at standard resistance (hotter LR parts can be used on 450mah+ batteries and will use charge up faster)
Best? I won't get into that. Everyone has their favorites. What I listed are popular.