any novel where a modern guy transmigrates and becomes emperor and has to deal with his harem, Empress, and different parties plots and schemes to kill him. would love something like the drama Secret of the Three Kingdoms where the emperors hidden twin brother replaces the emperor and who's intelligent like f and has a romance with the Empress who previously where left out in the cold by the previous emperor. However, I'd prefer a modern guy transmigration to see how a guy from our times would solve various schemes and silly superstition and stuff like that.
I totally focus on the "modern guy to past" and forgot about "being the emperor" part. Still, at around half part of the novel, the MC becomes very influential (General, friends with chancellors and kings).