The difference between these cameras is that SLR and paraxial are actually two different types of cameras. SLR is the abbreviation of single-lens reflex camera, which means that there is a lens on the fuselage, and then there is a reflector in the fuselage to reflect the light from the lens into the pentagonal mirror at the top of the camera, and then enter the viewfinder to let the photographer see the image.
Paraxial means that there is a separate window next to the optical axis of the lens, which is parallel to the optical axis of the lens. Photographers judge the framing situation by the light of the optical axis next to them.
Micro-single is basically the product after the reflector and Wuling mirror of SLR are removed. After the light enters the camera, it hits the sensor directly. Some micro-singles look like SLR, but in fact they just add an electronic viewfinder to the fuselage.
Digital images are basically micro-sheets with fixed and unchangeable lenses, but generally for the sake of size, the sensors used are relatively small and the imaging quality is poor.
Last word of advice, young man, let's play SLR and buy Leica after retirement.