I don't own that tank, and don't have a specific answer to your question, but this review does mention how to coil the tank, and wattages to run specific coils.
Billow V2 Nano Review
As far as figuring out what is best for you, you'll have to do some experimenting. I'd take the wires you have, and input a resistance that you'd like to end with (target) and remember you are using two coils so resistance will be halved. You can try this using your 26g kanthal and 24 gauge nichrome 80, and see if you can find a build that might work for you with either wire, then start experimenting.
Sorry, it just isn't as simple as saying Build X to get Y, as you are the one who will be deciding what kind of ramp up you want (this WILL be based on total amount of wire used in your builds, so thicker wire will give you slower ramp up than thinner wire, and also on the properties of the wire. It's also hard to give you a target number that will "give you the best clouds and flavor" as these things are going to be subjective to you. I'd shoot for a resistance that you've liked before, and kind of go from there. You also will need to look at your build deck and chamber, and decide what diameter build is going to work for you as well. It's not difficult, but it all may require a certain amount of experimentation on your part. Best of luck. I realize you may well know some of this information (possibly) I'm just going on based on your original post, sorry if I have given you information that isn't helpful, or not what you need, I am sure others will be along to comment.
Best of luck,
Anna