The Druid Talent Tree for Costume Magni is identical to the Talent Tree of any other Druid.
In terms of applying emblems to a costume, you can only apply the BASE hero emblems.
To follow the “druid” path, just flick back & forth between the two talent trees & pick the appropriate nodes. The Costume’s talent PATH will be identical to that of the base hero.
E.g. I re-did the emblem path of my Lianna in order to optimise for the costume.
They are great stats aren’t they.
I don’t know the exact answer to your question, but if you click on the future greyed-out nodes of the talent tree you can see how much they add to attack, def and HP and then you can total them up yourself. Always fun to exercise the brain.
I love this part of the post !!