N/5 + 1 is just plurality.

"most" == majority == N/2 + 1

which is it, is it just that VCs want to see that there is a designated leader among the founders, or do they want the relative amounts of stock to not ever become an issue for the viability of the startup ?

mere plurality is risky, because any of the founders could sell their share to another, creating an ownership crisis where the nominal head of the company has a minority share.