What is the internal impedance of the ADC in a ESP32?

[Sprite]

Is it likely that an ESP32-C5 has an even higher input resistance than the "classic" V3?

I would not assume anything about the input impedance other than that it also will be high. Also note that it's allowed for these impedances to change (e.g. by a change of manufacturing process) without any indication, as long as they're better than what the datasheet specifies.