A Psychiatrist is a medical doctor (MD) who specializes in mental health and is covered by OHIP. They:
Provide assessment and diagnosis for mental health disorders
Assess the need for biological interventions, such as medication, to support well-being
Provide some psychotherapy (but mostly are not able due to time and OHIP constraints)
Some may be involved in medical research
A Clinical Psychologist is a mental health practitioner, who (usually) has a PhD in a specific field of research. They:
Provide detailed assessments for mental health disorders, in addition to learning disorders and other accessibility needs (A Psychoeducational Assessment is done by a Psychologist, not a Psychiatrist). They are not legally allowed to prescribed medication.
Provides psychotherapy
May be involved in ongoing research and teaching in the field, particularly around psychotherapy
A Registered Psychotherapist is a Master’s Level mental health practitioner, who has undergone intensive training in the act of Psychotherapy and Counselling. They:
Provide Psychotherapy and Counselling for all types of concerns, mild or severe.
Does not diagnose or assess for mental illness, nor prescribe medication
May be involved in research and / or teaching, and some do their Doctorate
Other health professionals, such as Registered Social Workers (RSW) and Registered Nurse Practitioner (RN) are legally allowed to provide psychotherapy as part of the Psychotherapy Act
Typically, one seeks out a Psychiatrist to receive a diagnosis and discuss psychopharmaceutical interventions. If one needs a Psychoeducational assessment, they will seek to work with a Clinical Psychologist.
For therapy, one can find high quality therapists, with extensive mental health training, whether they are Psychologists, Registered Psychotherapists, Social Workers or Nurse Practitioners. What matters most is their level of training and expertise in the concerns you particularly have.