I find similarities in these two dramas because they both take place outside of the palace. Also, the feel is quite gritty and the cinematography is gorgeous.

The romance is a slowburn and ML is quite a mystery.

Both of these dramas focus on firefighters/rescue team. Also the main characters meet after 10 years.

While the male leads are firefighters, the female lead in A Date With The Future is a reporter and the one in My Fireworks On Earth is a doctor.

In both these dramas, Male Lead is disguised as eunuchs to enter the palace.

Male lead suffers from mysophobia and female lead doesn't care getting dirty.
Female lead is fun and quirky while male lead is straight laced and cute.

Both dramas have similar settings :

The location : The action takes place on the ML's vineyard
The story : The heroines are forced to get in a marriage with the ML though the motives are different
The genre : Slap and kiss ; main leads bickering

In both dramas, the heros families are business rivals who try to one up each other.

The FL and ML both work in the family firm of their respective family and are competing.

Both dramas are romcoms centered on individuals working in a TV station as anchors or weather reporters.

Both these dramas are centered on a mythical
and immortal creature who used to be human and whose goal is to find the person who'll be able to help them end the curse they are subjected to.

The dramas are high-budgeted with good acting and high production value and cinematography.

Both these contemporary dramas are sequels of period dramas.
The common point is that the main leads features in the dramas are reincarnations of the prequels.

The difference is that Forever and Ever is a full fleshed drama while Good Bye My Princess: Special is made up of snippets.

Both these dramas are centered on a male lead wanting to avenge his sister's death.
Also in these dramas, the male lead tortures the heroine for her brother's wrongdoing.

While in Irrestible the main couple started by being in a relationship, in Game Payabaht the male lead approches the female lead with a purpose.

Both these dramas are centered on a male lead wanting to avenge his sister's death.
While in Irrestible the main couple started by being in a relationship, in Peek Hong the male lead approches the female lead with a purpose.

Both these dramas focusbon a strong female lead who is the CEO of a corporation.

Also, another similarity that can be noted is that in the two dramas, the leads enter a marriage of convenience which eventually leads to their falling in love.