I bring everything I know to whatever I write, and I believe the same of other writers. A person’s complete life experience forms the basis of authorial voice, in my opinion. To hold back any part makes a narrative feel contrived.
Protagonists don’t have to be likable. They just have to be compelling. The key characteristic of a protagonist, whether they are conventionally good or evil, is that the reader must be interested in knowing what they will do next, or how they will respond to what happens to them. I’ve mentioned elsewhere how much I detest all that ‘hero’s journey’ crap…