In our company we've tried everything - GPT, Bart and human writing. What works best for us is:
• Bart for value proposition for the target persona: ask what is the business consequence of not using your product or your product value.
• GPT or Bart for email structure and short, straight to the point emails.
• Human part - personalisation like including things you saw on LinkedIn, industry news, interested contact in common, etc.
• Once you learn the writing, practice the calls!
Hope it helps!