As described in the Signal Level of a Node documentation, the output strengths for the output pins of tri-state buffers are set to STRONG when they are enabled but set to HIGH-IMPEDANCE when they are disabled. The output pins of pull resistors, however, are always set to RESISTIVE.
Both the tri-state buffers and pull resistors have the ability to use a ground ref pin. A ground ref pin is required whenever a digital device is connected to an analog component. For more information, see When is Ground Ref Required? The symbols for these devices are automatically generated when the device parameters are edited, allowing easy design changes.