Bridal mask is probably the best" jeoson / japan" era dramas.. i just love it, i am not comparing these two drama for they are different in theme but overall here are the similarities i saw:
1- the jeoson / japan era.
2- the freedom seekers and under-covered agents plus the under-covered male / female lead.
3- the bromance <3 (esp Chicago typewriter).
4- the war romance.
5- the old story of the male saving the female (become their first love).
6 - the goal of freeing the country which comes before anything else.
basically the main points u will notice too if u have seen both dramas.
and they are both worth watching although to me bridal mask is on a different level <3 :).