Leica Q-P has a
24.0MP Full frame (36 x 24 mm ) sized CMOS sensor and features Maestro II processor. On the other hand, Fujifilm X100V has a
26.0MP APS-C (23.5 x 15.6 mm ) sized BSI-CMOS sensor and features X-Processor Pro 4 processor.
One other difference between these two cameras that is worth mentioning is that Fujifilm X100V'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 moiré occurring in certain scenes.
Below you can see the Q-P and X100V sensor size comparison.
As seen above, Leica Q-P has a 2.4x Larger sensor area than Fujifilm X100V. 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.