A "Sunday bag" is a type of lightweight golf bag that is specially designed to be easy to carry, hold between 6-10 clubs, all while having enough storage for all your basic golf needs.
Although cart bags often come with a shoulder strap, as the name would suggest, cart bags need to be placed on a cart to move them around the golf course as they don't stan upright on their own.
If you are a frequent golfer, tend to pack a lot in your bag, always have a caddy, and don't mind lugging the bag around for a round, then a staff bag might be worth the extra weight.
Typically a pencil bag can hold up to 14 clubs. Despite being lighter and thinner, they have an excellent amount of space.
When carrying a golf bag with one strap, you generally want to use your dominant shoulder as it will be stronger and have stamina. Even so, if you start to feel your arm get tired on one side, you can easily switch shoulders to give your dominant arm a rest.