For a start, I won't travel with a wheeled bag when doing One Bag.

That saves a lot of weight.

I have a Red Oxx SunChaser as my primary bag, a small purse that can fit into the SunChaser is needs be and a superlight weight bag in the SunChaser with critical items if I need to pull that bag out for forced gate checking.

Often my super light bag is a US Post Office large mailing envelope.

I have also been allowed a shopping bag on some flights. But you never know.

All of my stuff including purse weighs less than 17 pounds when I'm doing One Bag.