The first story (which consists of the first two chapters lead by the title 5 Seconds) was delicious and a refreshing new take on "heat"! (not omegaverse though) Honestly I'm only disappointed such a great new plot device was only given a short-story to shine in.
I give story #1 4/5 stars for sexiness and a refreshing idea (hopefully the mangaka comes back to that and develops a longer story!).
The second story is even shorter (1ch), and is twincest. I didn't like it as much as the first (and my mind really doesn't pull positively for incest-stories so that was already working against it) but it was honestly sexy and had great art, too.
I give the second story 3/5 stars for sexiness and making the drag-queen-twin the seme. Would have given it 4 stars if they weren't blood-related and it were longer, and 5 stars if it was easier to follow when it starts out.
5 Seconds