Both are a love story between a human and an immortal being. Both feature grim reapers as main characters, and common themes of life and death, loss, grief, and reincarnation. Both have bittersweet, very similar endings.

Both are historical dramas with a princess FL. Both MLs have suffered trauma and loss, and find their strength and healing in their love of the FL. Both dramas have surprising and unexpected happy endings of both MLs faking their deaths after a severe injury, and the FL going off with them to live a quiet life, despite being loosely based on tragic historical events.

Despite the difference in settings and plot, in both one of the lead's father murdered the other lead's family as well as trying to kill them. Despite this, the two leads become each other's healing.

In the early episodes of RFY, the relationship between the main couple is very similar to the secondary couple in HOL. The FL vs. SFL are princesses being forced to marry a prince of another kingdom, and the ML vs. SML is a guard of lower status who initially refuses to admit his love for her despite fighting and risking his life to protect her.

Similar pacing and vibes with a noble family/families as the main characters, and multiple couples in both, each with their own storylines. FL frequently solves the problems of the family she married into.

FLs are high-spirited, independent minded princesses determined to make their own choices when it comes to life and romance. Both MLs are excellent fighters who are devoted to the FL.

Both are historical set, somewhat slow paced, but engrossing. Both MLs have some sort of supernatural power. Both FLs are their second, instead of first love.

Both have a ML with regrets and a short lifespan. Their only hope for a cure is in a vault that can only be opened by pieces of a treasure (jade vs. glazed armor) that multiple people are fighting over. Both are historically set with fantasy elements.

MFMR is much, much lighter in tone than WOH, though.

While MFMR is much lighter in tone and shorter than LoF, both MLs suffer from a "cold poison" and the FL is willing to go to great lengths to try to save him once she finds out. Also the plot involves trying to locate and put the pieces of a treasure together.

Completely different in tone and length, but both feature a ML with a demon side that keeps trying to take him over and a "displaced" FL (through time travel or resurrection) who tries to save his human side.

Both MLs have facial scars and are very warm hearted but people misjudge them and are afraid of them. They hang out or work at a restaurant where the owner/workers are their friends. The main female character has a special trait (visual impairment vs. reading minds) which leads her to not misjudge the ML like most people do. Both shows have a similar quirky humor and some sweet moments.

Both dramas have gorgeous cinematography, beautiful soundtracks, and a haunting tone. The romance between the main couple is star-crossed and tragic and the ending open/bittersweet.