What other executive powers are inherent to the legislature?
The inherent power of Congress is to subpoena for info that would faclilitate legislating.
Which is one reason this committee is illegitimate, it is acting as LEO investigation, not as legislative education.
At any rate, the inherent power to subpoena can be and is abused, and the rest of the system goes along with it, showing that the rest of the system is illegitimate too.
There is a moral obligation to reject illegitimate orders.