Also, Kami of worldly things (plants, animals, furniture) tend to be either animalistic, without a lot of higher mental functions (this is especially true for spirits of non-living things), or servants of "higher" Kami (foxes are all servants of Inagi, for instance). You're basically asking about the scions of the messengers: Yatagarasu, Kirara, and Mokumoku are technically kami themselves, after all. In another couple hundred years, machine kami might have developed enough lore for full sapience, but for now the question kinda squicks me.
To Sum Up: Animal kami are fully sapient (crows, rabbits, snakes, foxes), but of low inherent magical power (their magic is directly proportional to age) and are usually servants of a higher power anyway. Machine kami are animalistic: creatures of base instinct, lacking higher mental functions. Plant kami can be fully sapient (edit: and highly magical), but are otherwise simply massive and elderly plants of various kinds and so ill-equiped to go about hybridizing themselves with humans.
To Sum Up: Animal kami are fully sapient (crows, rabbits, snakes, foxes), but of low inherent magical power (their magic is directly proportional to age) and are usually servants of a higher power anyway. Machine kami are animalistic: creatures of base instinct, lacking higher mental functions. Plant kami can be fully sapient (edit: and highly magical), but are otherwise simply massive and elderly plants of various kinds and so ill-equiped to go about hybridizing themselves with humans.