Power Couple

Currently watching Secret Forest and I love how they work together. 

I don't know if this fit what you want since i didn't watch when a  snail falls in love  
i remember you
vampire prosecutor 
love me if you dare

Heh. I also immediately thought of Secret Forest because of the drama example you gave and the description. 

Otherwise, the only couples that I can think of in the drama that I've seen are the main couples in Five Children, Kill Me Heal Me and perhaps Healer. These couples were for the most part harmonious in the drama even if conflicts arose in their relationships while facing challenges and pursuing goals. Each person in the pairing also had his/her own strengths and was not really overshadowed by the other half of the couple.

It's funny that there are multiple LMIYD recs, because this is actually my anti-example. It's a good drama, but I felt like they put the male lead on a very high pedestal--this omnipotent genius that nobody could match up to, much less the assistant female lead. This is why I preferred When a Snail Falls in Love; both premises are very similar, but the latter does a much better job at making the leads actually need each other's skill and insight (imo). 

Felt the same with I Remember You as well (omnipotent genius male lead that doesn't actually need the female lead). Again, good drama, just not a power couple for me. 

I think I am just extraordinary picky lol. Other dramas that fit for me were:
Empress Ki
Let's Fight Ghost
General and I  

And thank you for all the recs above! 

Strongly recommend Signal although there is no/very less romance.

I recommend Surgeons. It's a c-drama. Both female and male leads are very good, well-developed characters and their skill levels are very similar. They often have to work together and they become romantically involved well before the drama ends. They are a true power couple!

Thanks to everyone for their suggestions!