Canon R has a
30.0MP Full frame (36 x 24 mm ) sized CMOS sensor and features DIGIC 8 processor. On the other hand, Canon R5 C has a
45.0MP Full frame (36 x 24 mm ) sized CMOS sensor and features Digic X processor.
Canon R5 C's sensor provides 15MP more than Canon R's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the EOS R and R5 C sensor size comparison.
Canon R and Canon R5 C have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Canon R has 48% larger pixel area compared to Canon R5 C, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.