I cannot explain the former as I'm still confused by EPH's algorithm (which would be a worse thing if it weren't that Dave McCarty has the code that counts the nominations - but I should probably attempt an independent implementation for the same reason we have two vote counting programs). But my understanding is that EPH+ changes how a given nominator's nominations are distributed utilizing a known therom from voting theory.

3SV will work the same with EPH as it would have with the current system. Now it is just that the long list of 15 and the short list of 6 will be generated using the EPH rules.