Question

How good is a love ball on a Pokemon of a different gender and how good against a genderless?

Answer 1

Against the same gender: 1*

Against the opposite gender: 8*
(only for the same species.)

My best guess, would be that, if the Pokemon are different genders, but a different species, then the catch rate would be 4*.

Answer 2

In short, not very good most of the time. It is only effective if the opposing pokemon is the same species as yours and opposite gender. In this case you have 8x higher chance of catching it.

For all other situations it works the same as a PokeBall. For example, different species opposite gender, same species same gender, genderless, they all only have the 1x capture rate.