In my opinion the thoub is not a must and me personally go to malls some times with sport clothes and some times casual trousirs and t-shirts.
Fubar it is up to the Qatari man and woman, because believe they all wear things which matches religion.
Fubar a restrict person will say jeans are forbidden and others such as T-shirts, I hope you can read more on dress in Islam and be more flexible person.
I am very flexible I do not say for a woman who is not wearing Abay bad thing, because I know 100 % some women who does not wear Abaya is better than some women who wear Abaya and vice versa.
A person is better than others when it comes to treatment and behavior and attitude.