Is there a 7-11 and/or a place like Boots or Watsons in the airport?

Yes, yes and yes.

On level 2 and 3.

At the check in levels there's a Boots and Family Mart at the end near the immigration counters, and there's also 7-11s around the place.

Airside in departures there's a Boots down at gate F/G.

At the check in levels there's a Boots and Family Mart at the end near the immigration counters, and there's also 7-11s around the place.

Airside in departures there's a Boots down at gate F/G.

in departures there is also a family mart.

Just be aware that the BOOTS inside departures marks-up normal prices by about 3 to 4X.

I bought a pack of Ibuprofin there that normally cost me B30 at most Boots: B100 inside departures.