Physician Assistants work in a collaborative/supervisory relationship with a physician. As a new PA graduate this PA/MD relationship usually involves a little bit more direct supervision. As the PA grows in knowledge, skills base, and judgement, the degree of autonomy increases. PAs work within a model of physician delegation. The supervising physician delegates clinical tasks to a PA (assessment, diagnoses, treatment, procedures, prescriptions, etc.).
Autonomy is based on what is negotiated or agreed upon by the supervising physician and PA. This is outlined in a supervisory agreement, or in Ontario this is outlined in a medical directive.
 About PAs https://capa-acam.ca/about-pas/
Nurse Practitioners are independent practitioners and work under their own authority as regulated health care providers.
NPs would require medical directives only for those controlled acts which we are not able to perform on our own. While this is very limited, depending on the practice setting, an NP in Ontario would require a medical directive to order a CT or MRI for example, because this is not currently part of our scope of practice. In other provinces this is part of the NP role though. So the need for medical directive is quite limited.
Once you pass the licensing exam and receive your Nurse Practitioner Designation, you can open up your own practice. Very few NPs open an independent practice, as this requires patients to pay them for their service. In Ontario, Nurse Practitioners do not bill OHIP and are salaried employees. This may be different in other provinces such as BC, but the majority of NPs in Canada are not able to open their own practice the way physicians do.
There are no requirements or parameters around what you do once you graduate. Of course, when you are a novice NP, your knowledge skill and judgement will be more limited. Nurse Practitioners do not require medical directives to function autonomously.
There are no requirements to have a formal relationship with a supervising physician the way PAs do, but NPs often work in teams with physicians anyway – just like in Community Health Centres. So although as Nurse Practitioners you don’t require physician oversight or medical oversight, you are still working with a team and consulting with other team members as required. Most physicians are happy to be consulted by a NP or work with NPs if they needed assistance with a patient.
NPs are also able to open up their own clinics independent of physicians. These are called and are funded by the government. There are 25 NP-led clinics are in Ontario, serving about 90,000 patients right now. Their budgets quite small compared to funding available to other programs, but the Ontario Government will increase funding and expand the Nurse Practitioner model.