Generally (in my experience) if your focus is on flavor, getting the lowest-resistance coil and vaping it with wide-open airflow isn't going to give you what you want.
The first thing I would do, and this is just me, is I'd try the 0.4 ohm coils for the NRG tank, and I would close the airflow up some. Play with your wattage - start out at, say, 40 watts, with airflow about halfway open, and see how that is. If it isn't warm enough for you, bump the watts up to 45, and open the airflow just a tad more. You can go up or down, depending on how you like to vape, but if you'll be patient with it, I bet you will find a sweet spot and that tank will vape just fine.
One thing about leaking from a bottom-airflow tank: it helps to be very specific about how you refill the juice. Try the following steps:
1. If your coil is new, drip juice into each of the holes around the outside housing until the cotton looks well saturated. You can also drip about five to seven drops down into the center of the coil. Then reassemble your tank. Note: it's important that the cotton is good and wet, otherwise when you start vaping the new coil it will scorch.
2. Close the airflow all the way.
3. Open the top cap and refill juice.
4. Replace the top cap.
5. Turn the tank upside down, with a paper towel or tissue handy to catch any juice that dribbles out the drip tip.
6. Open the airflow.
7. Slowly turn the tank right-side up again and thread it on your mod.
8. Vape it for at least 10 hits or so, right away, so the vacuum inside the tank gets set properly. (At this point, if the coil is new, you'll want to start out with wattage a little lower than normal, for maybe the first half dozen hits or so, just to be sure you don't trash the coil.)
Good luck, hope this helps. Let us know how it goes for you.
Welcome to VU!
I have better luck with all types of tanks if I do not fill them with juice and then just let them sit without being vaped.