Both Canon RP and Fujifilm X-T3 have 26.0 MP resolution sensors but Canon RP's sensor is Full frame (35.9 x 24 mm ) and Fujifilm X-T3's sensor is APS-C (23.5 x 15.6 mm ).
Since Canon RP's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Fujifilm X-T3.
One other difference between these two cameras that is worth mentioning is that Fujifilm X-T3's sensor doesn't have an anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moire occurring in certain scenes.
Below you can see the EOS RP and X-T3 sensor size comparison.
As seen above, Canon RP has a 2.4x Larger sensor area than Fujifilm X-T3. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.