I haven't tested extensively but I've been fixing some interactions between these, the idea is to support it yeah. Currently has no skill trees for tarnished characters though.

Epiphany has some code related problems that can result in frame loss. Is there any impact for not using epiphany with your mod?

It may be good to have mod compati elite patches as separate files or something because a number of mods are very inefficient and/or buggy.

It shouldn't affect framerate at all as it generally just adds a few items/monsters/etc to existing lists, mostly to avoid certain interactions that might crash or softlock the game.