The Infinity + Trance + Radiance genes are rather costly and will quickly eat up your AP. If you use Failure + Infinity, you will still have a controllable Kaiser form at nearly half the AP cost, although Kaiser Breath looks slightly different.
Infinity + Failure allows you to control Kaiser. Infinity + Radiance + Trance also allows you to control Kaiser, but costs more and is stronger.
To easily defeat Myria, have Ryu learn Aura from the master Ladon, transform into the Kaiser Form 2 (Infinity + Trance + Radiance), then use Aura.