Manual Focus Mode You can use the manual focus mode of your camera to Zone Focus which is a popular technique used in street photography.
Live-view Live view lets you take photos without using the viewfinder which makes you less obstrusive and this works very well during street photography where you don't want to get people's attention.
Face-Detection Focusing Face detection focusing mode is very helpful in the street scenes where you focus on a face, since you can concentrate on framing and other adjustments while the camera handles the focus for you.
Image Stabilization Image stabilization reduces the effects of camera shake at long exposures and long focal lengths in street photography thus ensuring sharper photos.
Fast Lens at Wide: f2.80 Wideangle is used more common then the tele angle in street photography. A larger aperture will give you extra shutter speed without boosting the ISO in order to reduce blur in low light conditions which is a common scene in street photography.
28 mm - Good Wide Angle Coverage Having a good wide angle coverage becomes very important in street photography.
RAW shooting capability RAW files contains much more color information compared to JPEGs, and gives you more room for post processing without significant quality loss. They provide wider dynamic range and option to recover shadow and highlight clipping to some degree.
Small Body Small body of Ricoh GR III will get less attention from the people in streets and give you an amateur look, which is indeed an advantage for street photography.
Large APS-C (23.5 x 15.6 mm) sensor Large sensor in Ricoh GR III ensures a good low light image quality compared to smaller sensor, and it also provide shallow depth of field and a nice blurry background when needed.