Glad you liked Three Lives Three Worlds.
It's one of my favourites too. I cried in the second last chapter, where Ye Hua 'died'.
click to show/hide spoilersYe Hua is brought back alive in the last chapter. The actual ending of TLTW is happy.
I actually haven't read that much Chinese novels, but I'll do my best to recommend.
I haven't read all of Yun Zhong Ge/云中歌 (sequel to Da Mo Yao) but due to it being written by Tong Hua as well, it should focus on the OTP quite strongly. I would also recommend Bu Bu Jing Xin/步步惊心, if you haven't yet read the book.
In my opinion, 花落燕云梦 focuses quite a lot on the OTP (Tang Rui and Zhu Di) as well, but it's really 虐. The female lead in here also time travelled back, to the Ming Dynasty.
Plot:
研究明史的现代才女林希,因为未婚夫飞机失事去世,选择殉情自杀。结果她的魂魄却飘逸穿越了时空,来到明朝 ,变成唐门圣女唐蕊。在这里,她遇到了貌似未婚夫的三皇子朱枫和神似未婚夫的四皇子朱棣。朱枫的温文、朱棣 的强取,都渐入她的心里,茫然中她卷入了朱家众皇子皇孙的皇位争夺战中。一时之间朝堂之上风起云涌,江湖之 中刀光剑影,后宫之中尔虞我诈。面对权力和爱情,面对阴谋与手腕,她将选择何去何从?最终权归何人,情又归 何处?
Modern woman Lin Xi (who studies Ming history) chose to suicide because her fiance died due to a plane crash. Yet her soul time travelled back, and came to the Ming Dynasty, where she was the female saint Tang Rui, of the Tang family. Here, she met someone who appeared to bear a striking resemblance to her fiance (Third Prince, Zhu Feng) and someone who had the same temperament as her fiance, Fourth Prince Zhu Di (future Emperor Yongle of Ming). Zhu Feng's gentleness, Zhu Di's arrogance all entered her heart, and entered the war for the throne between the sons and grandsons of the Zhu family. All at once, the court became very turbulent,
Jiang Hu started stirring, and the harem was full of dangerous intrigue. Faced with power and love, what will she choose? In the end, who will acquire the power, and who will acquire the love?
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The books on my list (except 华胥引,琅琊榜,**) focus quite a lot on the OTP.
**The books by 倾冷月 probably not as much, because her books are a wuxia genre. Although towards the end, it focuses on the OTP. E.g. 兰因璧月's OTP is first 相杀,then 相爱.