All straps should be adjustable. Look for crisscrossing internal straps in many of the garment bags. These straps help hold your clothes in place so they don't wrinkle. Brass and nickel hardware is beautiful and will hold up to a lot of punishment. These are also very reliable, and can be easily replaced in the rare occasion that one would fail.
Garment bags have an exterior top hook that allows the entire bag to be hung, open, in a closet.
That hook needs to support the weight of all your clothes, plus the weight of the bag, so it better be sturdy. It should also retract into, or snap down tightly against, the outside of the bag when in transit.