1. Between a female High Elf and an Elin, I'd prefer a HE Mystic. Not to say that Elins aren't adorable and they would fit the class, but I hear there's a lot of clipping in their armor because of the shorts. Plus, the HE armor is beautiful. The only reason I wouldn't pick one is the same reason I wouldn't pick a Castanic- they're oversaturated. At least on my server (Celestial Hills).

2. A Castanic Warrior is clearly the most used combination. They're nice and all, but if you want to stand out a little, I wouldn't go for a Castanic. I play a Human, so maybe I'm a little biased, but I'd say go for them especially if you're planning on doing PVP.

In the end though, it's your decision. The racials really don't matter and the only racial I've ever used on my Human Mystic is Velik's Horn. So look at that link to the armor gallery someone posted earlier and choose that way. After all, it's the look of the character that matters. Also, you could view some videos on youtube to get a feel for the animations of the different race/class combos.