Panasonic FZ80 has a 18.0MP 1/2.3 (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features Venus Engine 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.
Fujifilm X100V's sensor provides 8MP more than Panasonic FZ80'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.
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 FZ80 and X100V sensor size comparison.
As seen above, Fujifilm X100V has a 13.1x Larger sensor area than Panasonic FZ80. 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.