Like any other superline, you should purchase it by diameter, not breaking strength.
It is rated closer to its real strength than most other superlines. Similar to Daiwa Samurai.
I use the 24# for light to ultra light and the 40# for heavier work. Works great and casts really well.
I use the FG knot and Uni-Uni knot when I attach a fluorocarbon leader. I use the FG knot with my micro guide rods.
Humminbird Helix 12 SI, 1198c SI, 1198c SI, ONIX 10 SI NT, 360, RC-1