The maximum clock frequency for the TPIC6C595PW is 30 MHz.
Yes, the TPIC6C595PW can be used as a level shifter, but it's not recommended as it's primarily designed as a shift register. For level shifting, consider using a dedicated level shifter IC.
To ensure that the output pins are in a known state during power-up, use an external pull-up or pull-down resistor on the output pins, or use the output enable (OE) pin to disable the outputs during power-up.
The TPIC6C595PW can sink or source up to 25 mA per output pin.
Yes, the TPIC6C595PW is 5V tolerant, so it can be used with a 5V microcontroller and 3.3V peripherals, but ensure that the output voltage does not exceed the maximum rating of the peripherals.