new to the shield, not to rooting but need help

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OK, so hey guys and girls, I have the nexus 6p and have excellent experience with rooting android....I have actually built my first google stock ROM for nexus 6(shamu) and work on other teams for beta testing etc. In saying all that, I have not strayed away from moto, google, or Sammy software. I am buying a nvidia shield from swappa, but atliitle confused. Is their only 1 nvidia shield tablet? If not, which ROMs are compatible with k1 variant?