Yes, one by one, in Settings → Cyber Mission, Notifications section:
the reminder sent 14 days before the deadline (Follow-up reminder);
the last reminder, 3 days before (Last reminder);
the manager alerts (Manager escalation), at 14 days and at 3 days.
Social nudges, linked to the progress of squads and the company, are disabled separately with Social nudges.
The introduction message and the new mission notification are always sent: they are what let the employee know their mission is available. See 3️⃣ How to Configure Cyber Missions?.