The Deer and the Cauldron (2014)

Both are the same, just filmed differently. Have the same background information and it the 2020 is a remake. The 2014 version explains more and gives more information and details that are shown in the 2020 version. I think it is best to watch the 2014 version and then the 2020 version, if you want background knowledge.

Both the Deer and the cauldron and Demi Gods and Semi Devils are jinyong's novel, tbh some of the martial art in Deer and the cauldron is from Demi Gods and semi Devils but much much weaker, even jinyong himself said it. Most of the casts are similar especial the actress are almost the same and male lead Han Dong. The director for both of this Tv series is Samson Lai Shui-Ching and he also acted as "Ao Bai" in The Deer and The Cauldron and "Wang jiantong" in Demi Gods and Semi Devils

Both stories are based in Qing dynasty and under Kang Xi's rule. Both mc form an unlikely friendship with the young emperor. Both mc try to over throw Qing dynasty. Dragon Pearl is very similar to a remake of the Deer and the Cauldron with a female lead.