In many countries if you have a company laptop then everything on that laptop or done on that laptop belong to the company. They are unlikely to be spying on your directly, but they will often have administrative access, will perform backups to ensure continuity of business data you are working on etc. If you leave and start a competing company someone in IT is going to get a call asking them to check your archived data (email, etc.) to see if you were working on this new company while using old company equipment or during old company time. If they find evidence of this then in many jurisdictions you are going to be in trouble...

Save the headache and use your own equipment. At the very least have a personal VM that you run to do your personal work on.