It seems to me that trying to create a tulpa is like trying to take a shortcut with mental discipline. It seems strictly better to me to focus my effort on a single unified body of knowledge/model of the world than to try to maintain two highly correlated ones at the risk of losing your sanity. I wouldn’t trust that a strong imitation of another mind would somehow be more capable than my own, and it seems like having to simulate communication with another mind is just more wasteful than just integrating what you know into your own.
Thinking about it, it reminds me of when I used to be Christian and would “hear” God’s thoughts. It always felt like I was just projecting what I wanted or was afraid to hear about a situation and it never really was helpful (this thing was supposed to be the omniscient omnipotent being). This other being is the closest thing to a tulpa I’ve experienced and it was always silent on things that really mattered. Since killing the damned thing I’ve been so much happier and don’t regret it at all.
That isn’t to say it has to be like that, after all in my experience I really did believe the thing was external to my mind. But I feel like you would be better off spending your mental energies on understanding what you don’t or learning about how to approach difficult topics than creating a shadow of a mind and hoping it outperforms you on some task.