Both Sony RX100 IV and Olympus PEN-F have 20.0 MP resolution sensors but Sony RX100 IV's sensor is 1 (13.2 x 8.8 mm ) and Olympus PEN-F's sensor is Four Thirds (17.3 x 13 mm ).
Since Olympus PEN-F'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 Sony RX100 IV.
Below you can see the RX100 IV and PEN-F sensor size comparison.
As seen above, Olympus PEN-F has a 1.9x Larger sensor area than Sony RX100 IV. 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.