Pretty much personal preference, but we leave the windows and the roof vent open if it is too warm. Roof fan is noisy even set low.
We have used the AC a few times at night, but only when it is humid outside. Spent two nights camping in Charleston, SC. 100% humidity. AC made it tolerable.
Thinking about getting a quiet roof fan.
As for safety with windows open, they don’t open much. Anyone/thing wanting to pry a window open wouldn’t really need it to be open. You could probably rip it open with a screw driver or fingers if you don’t mind breaking a nail.