As the title says. Im New into Only war but very firm in fluff.

Any advice on running a light infantery sniper squad?

We use the rules of the 5th Cyprian hunters.

May the God-Emperor have mercy on your souls.

I dont envy anyone playing a Ratling regiment. Pretty minmax and awful. Still, are you looking to learn about anything in particular?

Well according to the rules they use all the guardsmen classes without the Support classes. So no Ratling sniper in a Ratling Regiment. Snipers are then everyone as sarge, medic, heavy etc. all from the shield of humanity book.

My question is what I should be aware of in the official adventures if I have no real hard close combat hitter and they have only flak vests and helmets.

Only important difference to note out of hand is that they're going to have an exceptionally high mortality rate. Ratlings kind of die stupidly easily. The official adventures are written with light infantry in mind.