I would add that REO's are one of the safest mech's around, they are fitted with a hotspring that will collapse in the event of a hard short. They have plenty of venting, especially the SL versions.
I have tried tanks and rda's and found the rda's to be much easier to build on, they are less prone to problems with wicking. With tanks its a fine line between dry hits and a leaking gurgling mess. Dripping is great around the house but a pain in the backside when you are out and about. Once you have your build and squonking technique sorted a mechanical bottom feeder is just about as easy and bombproof as you can get.
In terms of battery safety, buy decent quality batteries and stay well within the CDR and you will be fine. Poor quality batteries in either a mech or regulated mod pushed beyond the limits can and do vent. I tend to keep below 50W when using a single 18650 battery. Bear in mind that a high output regulated mod can draw high current levels from a battery just the same as a mech. Bottom line is less current drawn equals less risk.
