I haven't watched a lot of Chinese (mainland China) dramas, when it comes to Mandarin-speaking dramas I usually watch the Taiwanese ones. Period/historical dramas too, unless they are airing on my local TV (which then maybe I will watch it), I don't go online and search for them.
But there are some that I actually enjoyed, like Xiao Yu Er Yu Hua Wu Que/The Invincible Duo, starring Dicky Cheung, Nicholas Tse, Fan Bingbing etc. And also The Legend of the Crazy Monk series, starring Benny Chan as Ji Gong/the crazy monk. So far it has had 3 seasons and I've watched the first and third one, all really entertaining. A classic one that I watched when I was a young child is the My Fair Princess/Princess Returning Pearl series, starring Vicky Zhao, Ruby Lin, Alec Su etc, but I'm not sure if you have watched it already. Next, there was this drama called Lotus Lantern which I also enjoyed. I don't know if you know the story of Journey to the West (Monkey God) story well but in Lotus Lantern there are some characters who also appeared in the Journey to the West story and I think it's cool how different stories can be sort of linked through some same characters. Speaking of Journey to the West, I liked the 2011 version (there are too many remakes of this lol, but I think it was the 2011 one...).
Hua Pi/Painted Skin also looks interesting, although I haven't watched it. It's based on one of the more famous Liao Zhai horror stories, and there were also 2 movies made about it. Also, an extremely popular one is Bu Bu Jing Xin/Scarlet Heart, which I was watching but didn't finish, it's really nice though! I'm just lazy lol.
I think I've only watched one modern C-drama from mainland China, and it's Let's Go Watch Meteor Shower. The producers were saying that it's not a remake of Meteor Garden/the Hana Yori Dango manga series (not licensed) but if I were to consider it as a remake then it actually be my favourite (I watched the Korean one and half of the Taiwanese one).
Anyway hope that you find something you like, with English subs haha.
P.S. Oh some time ago there was quite a big hype surrounding Lan Ling Wang, a mainland China-Taiwan collaborative period drama, staring Feng Shaofeng/William Feng, Ariel Lin, George Hu etc. I haven't watched it but you may want to check it out.