The majority of a neuron's transmembrane capacitance is attributed to the lipid membrane itself, so a lower density of ion channels should not appreciably alter capacitance.

Action potential rates and the ability to phase-lock to inputs are significantly affected by the membrane time constant. Generally, membranes with lower conductances at rest and during spiking will have higher (slower) membrane time constants. This isn't a straightforward explanation for the ability of human some neurons to phase lock to higher frequencies.

Impedance data across species relevant to this idea is in Extended Data Figure 2 and 5 of the paper.