By donating to funds instead of the charities themselves there are extra costs like the salaries of the fund managers. Is there any information about what percentage of the money is given to organizations? Is it more efficient just to donate to organizations directly?
Not exactly about efficiency, but in terms of impact I suspect that individual small donors would have more of an impact through directly funding small projects that larger funders such as EA funds can't or wont fund due to reasons such as the lack of capacity to evaluate them.
More reading on this here.
https://forum.effectivealtruism.org/posts/oHcRQsiDM9D76aENu/a-red-team-against-the-impact-of-small-donations