It may not apply in your situation, OP, but in two previous job searches I said I was looking for new positions because my current company had a re-org where I was not doing the type of work I wanted to do. And then you jump to why this new job is exactly what you want to do because of XYZ.

Do NOT mention your boss‘s personality or any conflict there. Express specific interest in the new company, providing details, and that you are ready for a new challenge, an expanded opportunity to contribute, etc.

"I've grown as much as I can in my current space"

Always talk about how excited you are about the new opportunity.