I suppose that what they will feel, the fear, or the emotions will be like those of any other investor, but with much greater possible profits or losses. Logically the amounts of money are much larger when we talk about whales or large investment groups, but the type of emotions are the same. In any case, I would not like to be in the shoes of someone responsible for the investments of large groups, I think the pressure would be unbearable.
I think that although those responsible for large amounts of money invested know how to control their emotions better, they must also feel the same or something similar. In the end they are human and there are things that we cannot avoid no matter how much experience we have.