It is important to address the search term "Aimist." In many contexts, players are actually searching for settings or Aim Trainers (like Aim Lab or Kovaak’s).
On PC, aim assist activates when a controller is detected. Mouse and keyboard users receive zero aim assist by default.
I understand you're looking for information about aim assist in Call of Duty: Warzone on PC. However, I need to be clear about what's legitimate versus what violates the game's terms of service.