Myrtle is a wonderful wood to work with. I used to bend it wet, but I have found that bending with no water actually works better- you get little to no cupping effect, whereas when I've used is wet it has often cupped quite a bit (not unlike maple).
Tonally, it seems to be bright and reverberant. I think it supports a crispness in the sound, and seems overall brighter than mahogany or walnut. I don't think that the bass suffers though- the high frequencies enhance the definition of the bass tones, and possibly the sustain as well.
Take this all with a grain of salt of course- I believe that most of the voice of the guitar comes from the bracing design and execution above wood choice, by a large amount. The wood just seems to accent or reinforce certain tonal aspects more than others depending on the species.
The most useful technique I have found is what I would describe as a sort of creative process of imagining the sound transformed by guitar strings/tension. If you tap every piece of wood regularly as you shape and construct the guitar, and also tap parts of completed instruments and various instruments you own, you begin to develop a sense of what the wood sounds like, and how that sound interacts with the vibration of strings under tension. As you refine this perceptive ability, you can begin to creatively imagine how each part will sound in the completed instrument by tapping as you work on it.
More specifically, by tapping I mean holding the piece of wood approx. 1/9 of the length in from the edge, lightly pinched between two fingers. This is derived from Young's modulus, or the vibration of free bars (which most pieces of wood resemble before being glued into a box shape). Each piece of wood will sound different, and some are more musical than others.
For example, dense wood such as rosewood and ebony tend to have a loud and clear pitch, like a marimba bar. Softer or less dry woods will have a muted, unclear note, and most other woods are somewhere else in between. I believe that all pieces of wood in an instrument contribute (even if an imperceptibly small amount) to the overall musical vibration/resonance, so in a handcrafted instrument it is essential to select the most musical sounding wood, or to shape the piece sin such a way as to accent that characteristic, regardless of the species.