I AM LET ME OUT. I liked them better when they were kids, Wan Yi looked more pure and sincere, Qin Xian was weird seemingly maso, but time and time again the story tried to refute it with a scene or two, but NOW!???

WAN YI IS AN ADMITTED SADO, THE STORY GOT REALLY KINKY AND... well Qin Xian is still not admittedly maso, but it looks like this is just a matter of time.

It was good while it lasted, Im out

Geez, its not that hard.

Qin Xian likes the real Wan Yi (the gentle and caring one, not the made up villain), but he can't get close to him because Wan Yi might get punished (electrocuted) or even end up dead if he fails his mission (completing the plot), so, to bend the rules, he is making Wan Yi use the magical wig to "transform" him into the female lead - Its stated in earlier chapters that a person can see through the wig's magic if they recognize who is wearing it. SOOO Qin Xian is not seeing Wan Yi as the female lead, but as Wan Yi himself - still, just the wig is not enough, so Wan Yi also needs to look like the female lead (this is the reason why he is also using women's clothes).
Anyway doing this Qin Xian helps Wan Yi complete his mission, prevents him from getting punished or killed, and he also gets to spend time getting close to him. So its a all win situation for him.

Yea, so 
No, Qin Xian is not into the female lead
No, he is not into traps

He likes Wan Yi and is only doing all of this to spend time being close with him and to protect him too.

The wig is a magical item the cat gave him, it transforms the protagonist into someone else, in this case the novel's female lead, aka the little girl

Its definitely not 19 days.
I don't think I've read this manhwa, can't help you op, altho Im quite curious about it now