Mix the leader bonuses, Civ bonuses or both. Balanced or overly OP. Your choice. My favorites overall are Gorgo and Seondeok. Killing a unit provides Culture equal to 45% of its combat strength, 2.5% extra for each promotion the Governor in your capital has. Gain a Wildcard slot for each Seowon that is adjacent to a natural wonder. Once per city and wonder. Max 3.