Both Sony FX2 and Sony A7 IV have Full frame sized 33.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
One other difference between these two cameras that is worth mentioning is that Sony A7 IV'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 FX2 and A7 IV sensor size comparison.
Sensor Size and Resolution Comparison image of Sony FX2 and Sony A7 IV Cameras
Sony FX2 and Sony A7 IV have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture.
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Sony FX2
or the
Sony A7 IV ,
including hyperfocal distance.
