It is similar since both dramas story plot is circled in a phenomena which it deals with strange objects and creatures from beyond the earth that will eventually enter earth to deal with humans plus the genre talks about supernatural, thrill and suspense.

Also this two dramas are both similar in terms of the occupations of the characters in the series how it will be interconnected with the evil spirits and mysterious phenomena

These two dramas are similar in such way on if VIP's female lead received an anonymous text message of her husband has a cheater inside the office in Show Window the female lead's mother called her to come over and witness something more than the fashion show and that is cheating of her husband

Both dramas are similar because it shows prostitution and hardships of a student it can be through outcast, being bullied abd many more

I watch the both of the dramas and its very similar by helping a person in their darkness days and be able to conquer it the leads became their shoulders when they feel lonely. Every characters in two dramas are lonely and in pain because of family problems, missing their love ones and being traumatize from the past, I recommend you to watch both of the dramas

There both have the vibes of a same theme where Hotel Del Luna we all know a woman from the past who commited a sin and the punishment is to live more than 3000 years if I remember? its 3000 or more or less? and she was brought in the living world to help those dead people with their grudges in human beings while on the other hand Mystic Pop Up Bar is similar by in the past specifically in joseon era where the female lead commited a sin and that is she killed 100,000 people including her baby inside her womb not realizing she is pregnant and killed the sacred tree and to reincarnate she was delivered in the living realm to help the people who are in grudge and a special case helped her in her journey to reach 100,000