It's the same story, same characters.
But "The Palace" focus on 13th life and relationships, while it's in "Scarlet Heart" just a side story.

Both movies talk about the same family, it just "Time To Love" is about the 4th and 14th prince, while "The Palace" focus on 13th prince relationships.

Both have spirits that appear after dying and act like a living person, though this one not a comedy at all.

In both movies the heroine travel to the past and found herself as someone already living in that era.

Bothe movies have the concept that someone from present and past can connect with each other.
Even though the genres of the two movies totally different.

The male lead here also rent a woman to pretend to be his wife in front of his family and eventually fall in love with his fake wife.