Yep, Salesloft does require you to create a contact before being able to enroll into a cadence. You can then use the person Id it returns or use the Lookup Person to retrieve it, then add them to the cadence.
Yes, if you mean you have different cadences like one for C-level and one for Directors for example, you can create separate Add to Cadence columns and use conditional formulas so each get added to corresponding sequences.