What's the difference between schizoid and schizotypal? can one be both?

Personality types: These are descriptions of personalities. You don't so much "have" them as "be" them. They are very similar. Neither is a social person. Both may have unusual interests and ideas and behaviors but if they are not unhappy or causing major problems for others - it is just fine. Many do well in technical and other non-public careers. These are concepts - not actual things.