Fujifilm X-T4 has a
26.0MP APS-C (23.5 x 15.6 mm ) sized X-Trans CMOS 4 sensor . On the other hand, Leica CL has a
24.0MP APS-C (23.6 x 15.7 mm ) sized CMOS sensor and features Maestro II processor.
Another difference between these two cameras is that Fujifilm X-T4's sensor lacks 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 X-T4 and CL sensor size comparison.
Fujifilm X-T4 and Leica CL have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.