Garrett has high cheekbones, so to replicate them for your own Red Dead Online character you will want to move the dot to the left side of the center column of boxes, and position it so that the second line down from the top is just above the center of the dot.
Like his jaw, Garrett's cheeks are slightly shallow in the slider for the Red Dead Online character builder, it is also set on the left side of the fourth square from the left.
I decided to use The Chompers when I selected Garrett's teeth.
I decided to give Garrett the Long Right Parted hair style, but be warned that if you change this hair style in the game, as I did once for one of the daily challenges, it cost me 2 gold to put the hair back to this style at the barber shop. I have not changed his hair style since, so am not sure if that is still the case or not. Just... you have been warned.
I wanted to make Garrett's hair as black as possible, while still having the ability to make out some details to it, so I finally settled on color number 9 out of 17.
For the Facial Hair options I went with No Beard, which made the Facial Hair Color not selectable, and for the Facial Hair Stubble I selected Stubble to get the 5 o'clock shadow look of someone that tends to shave every few days with a hunting knife.
Eyes & Brows
Mouth & Lips
Upper Lip Shape
Lower Lip Shape
Jaw & Chin
Ear Shape & Size