Both Fujifilm GFX 100RF and Fujifilm GFX Eterna 55 have Medium format sized 102.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
Another difference between these two cameras is that Fujifilm GFX 100RF'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 GFX 100RF and GFX Eterna 55 sensor size comparison.
Sensor Size and Resolution Comparison image of Fujifilm GFX 100RF and Fujifilm GFX Eterna 55 Cameras
Fujifilm GFX 100RF and Fujifilm GFX Eterna 55 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
Fujifilm GFX 100RF
or the
Fujifilm GFX Eterna 55 ,
including hyperfocal distance.