There is no difference depending on the resistance because the thermal time constant is based on the change of the environmental temperature. Regarding the size, it depending on the heat capacity of the device. However, in the case of chip type, it is used on board mounting. Since the heat capacity of the substrate is very large relative to the heat capacity of the element, and the thermal time constant is affected by the heat capacity of the substrate, there is almost no difference depending on the size of the thermistor element.