Top feed is generally used for dripping and the bottom feed is generally used on REO style mods..
You can still top-feed the bottom-feed cyclone, just take it off and make sure you clean off your positive post frequently. You will get a bit of leak down to your positive. If you ever get a bottom-feeder mod like the Reo or Bogger, you've already got a nice RDA for it.
the bottom feed has a hole that leads from the 510 thread into the positive post. You mount your coil in the top hole of the positive post, and is meant so that when you squeeze the juice bottle on a bottom-feeder, the juice travels up the positive post into the dripper.
The top-fed does not have the hole in the bottom and only has one hole to mount your coil in the positive. It can only be used for top-side dripping.
I have a piece of ss 1/16" tig wire I used on the last one, I have also used a small needle, and I use a set of hemostats to hold it while making the coil. I also rigged up a magnifying glass on a stand, so I can see what I am doing. I haven't tried the screw method yet, but I can see how that would make it easier, to keep the spacing the same. I am just not sure how many raps to use on 1/16" inside dia. using 32 ga. kanthal. I am using a provari to use this thing, I guess I want a coil at about 1.5 to 2.0 ohm coil. I am not sure about trying sub-ohm yet.
I may try the 1/8" next might make it easier to get my ohms where I want them.