Currently default is 100 enriched ore + 1 calcite → 500 molten metal. However I see that settings with very low bonuses might feel unbalanced, so I've added a Mod Setting that allows you to set the amount of ore used in the melting recipes.
Thanks again for the input!
Mod compatibility is a very time-consuming endeavor, especially for big mods like K2. It has been asked before, so I see the common desire and maybe I'll do compat at some point in the future. Currently I don't have the time to do so, but if you or anyone else is interested in providing compatibility, either as a separate mod or as part of EI, I'd appreciate that and encourage you to do so.