the Pentax Q system uses a tiny 1/2.3“ sensor which is 1/8th the size of the sensor used in Micro Four Thirds cameras and 1/13th the size of the the APS-C format sensor giving a 5.5x crop factor
interestingly some of the Pentax Q lenses incorporate a lens leaf shutter which allows flash sync to 1/2000th sec as well as a ND filter to allow wide aperture in full sunlight
these cameras have much smaller sensors than the above and thus allow smaller lenses and cameras but will never have the image quality or ability to blur the background as well as those cameras with larger sensors
they are designed for portability but the tiny sensor size means very limited ability to grow with these systems as a photographer
many may be just as well off using their iPhone