Honestly,if you want killer flavor and plenty of vapor I'd look into the subtank.The coils last and it's just an incredible tank,as for a box mod the MVP 20w is what I use and love.
RDA is for dripping directly on the cotton and RTA is a little of both a clearomizer and RDA in one.so yeah I guess they both are considered RBA's.You make coils and wick both.
I haven't built a vertical coil in a really long time.I personally don't see much difference in flavor between vertical & horizontal.But the vertical coil acts like a smoke stack and seems to produce a little more vapor IMO