The problem with your example is that you attempted to omit a relevant character with an irrelevant one. Psycho Man can not be used as any sort of evidence for Tutinax. The difference between them isn't a guesstimate, it's right on panel. We are no longer on the if it would work on Morg portion of the arguement, we are well past that. Let's move on and away from Psycho Man.
What we are arguing is how effective his fear emotion manipulative powers would work on a proven to be fearless character ready in an instant to jump to his death. The deepest embedded emotion known to humans is the urge to evade ones imminent death to the degree that it at times looks heroic. Well yeah, Morg lacked that response. Psychologically speaking, there was no fear response in the form of flight present within Morg. None. Can you draw water from a place that is absolutely devoid of moisture? Of course not.
So now that we've used on panel citations to emphasise the differences between Morg, and the very relevant Thor encounter with Tutinax, we should be able to move away from Tutinax's powers having any effect on Morg, because as I said, Morg to my recollection hasn't even one showing to draw upon the conclusion that his brain was capable of processing the fear response that a normal brain would. A Psychologist would immediately believe that he had a damaged brain. In his case it would be the amygdala portion.
Since we are no longer at that stage in this discussion, we should be exploring how the physically Low to Mid Herald level character known as Tutinax would do against the High Herald to Mid Trans character known as Morg. Let's face it, if Tutinax wasn't actively hindering Thor, he would've gotten his ass kicked in.
Wait do I have grounds to call Morg a Mid Trans level character? Absolutely, because we are using base Power Cosmic Morg, and the amplified Morg with the Power Cosmic and Water's of Life. In my opinion, Tutinax wouldn't even defeat the base version, so there's no need to delve into deeper water, by wondering how well he'd do against the amplified version of Morg.