Resolved fraction of CGM surface area as a function of kinematic resolution for velocity differences between H I and three representative ions: O VI (left), C III (middle), and Mg II (right). Each line corresponds to one of the six FOGGIE halos. The resolved fraction indicates the percentage of pixels where the velocity difference between the two ions exceeds the given resolution threshold and would therefore be distinguishable by an instrument. O VI shows the largest kinematic differences from H I. C III requires finer resolution (< 30 km s⁻¹) for broad coverage, while Mg II remains largely unresolved even at 30 km s⁻¹, reflecting its close kinematic alignment with Hα.