Both stories:
* are short and sweet
* have fantasy elements to aid the female lead
* have a pretty male lead and a plain female lead
* have a love triangle

Mengfei Comes Across and Oh My Emperor are similar, because these shows are both light, hilarious, and with a heroine that is cheeky and endearing at the same time. In both series the ladies dislike the leading men at first but love is in the air.

The Rise of Phoenixes made me think of Moon Lovers Scarlet Heart Ryeo. Both stories are about a prince who is abandoned by his imperial father, and mother. Both princes are used to fighting and murdering since their childhood. They have to compete with ambitious siblings in the struggle for the throne. Both are emotionally scarred by family issues, but super smart in plotting and survival. As for the love interests in both series, those girls are both too nice for their own good.

Mengfei Comes Across and Go Princess Go are both rom-coms set in ancient times. These shows mix modern day issues with the classic tale of court intrigue at the palace. In both shows the heroines are getting along with the concubines, in stead of fighting them until death. On the contrary, they really dislike their husbands, using their wit to avoid them or undermine their actions, but later on love comes by.