I firmly believe that Jin Guangyao and Jiang Cheng have no beef with each other for the majority of the timeskip. They both have traits that the other values in allies, if not necessarily in friends:
Jin Guangyao is extremely appropriate, considerate, hardworking, and never makes social situations worse than they have to be. I don't think Jiang Cheng would care that he has schemes or a fake smile because that's just everyone in the political world; it's not as if he has any delusions that the other high-ranking gentry are being fully honest and sincere with him either. On the contrary, he would pretty much respect the work ethic and understand that sometimes you have to do shit to get your dad to like you even when you know it won't work. In short, Jin Guangyao is unlikely to do anything to piss Jiang Cheng off, and at least is very kind to Jin Ling.
On the other side, Jiang Cheng is a man who is just not very dangerous if you understand him. You can say he's a man with a predictable temper, or you can call him easy to manipulate; either way, this works in Jin Guangyao's favour. Jiang Cheng is aware of Jin Guangyao's various social disadvantages, but is too pragmatic to try and exploit them, and is too single-issue to be a significant political opponent. While he does come from privilege, his personal life is so tragic that I don't think Jin Guangyao would feel moved to envy or resent him for his social standing, and at the same time he's a sect leader who actually does work instead of foisting it off on his servants or onto Jin Guangyao himself. In short, Jiang Cheng does not pose a threat to Jin Guangyao, and at least is very kind to Jin Ling.
Does this make them besties? That depends on how deep I am in the Chengyao sauce on any given day, but for sure they are not enemies up until the shit has hit the fan post-timeskip. They are essentially each other's least hated coworker