Im 5’7 as well, would recommend either the 30 or 25. My first speedy was a preloved DE classic 35.
After taking the 35 out to the mall and spending a whole day with it, I immediately listed it for sale that night. It’s an uncomfortable big bag. Don’t recommend it, especially if it doesn’t have a strap.
Highly recommend the size 25 bandouliere. That’s my most used bag for casual outings. For a work bag to fit the laptop, I wouldn’t recommend a speedy but a Neverfull.