Position size, AUM and number of securities

I find this concept particularly confusing
How does position size, asset under management, and number of securities impact the return of a fund with all the costs involved

Do you have a question example that asks it? Not sure on what you mean, i can only think about position size etc to aum amount of the fund.

Position limits might affect your return. But if all else equal, these should not impact the return to a large extent.