The OE ( output enable) is over voltage tolerant, high input impedance, active high enable pin for most of the TXS, TXB devices.
If the IOs must be in high impedance during power up or power down, the OE pin is recommended to have a pulldown resistor. Once the power is stable, the OE pin can be engaged( high level w.r.t Vcca) to have the normal operation of the device.
If the IOs are not required to be in Hi-Z, the OE pin can always be enabled ( either by a high signal or connecting to Vcca supply). Note that the OE pulldown resistor is only a recommendation and not a requirement.
TI does not have a device which is referenced to Vccb supply pin but can be connected to Vccb supply as OE is over voltage tolerant.
Refer to the FAQ here below: