SN74HCS164-Q1: R1 and C1 recommendation

This depends entirely on how fast the supply voltage rises. (When the supply reaches 2 V, the /CLR input must still be low.)

Just to expand on what Clemens said, you can determine the required RC values based on the supply voltage rise time using the following estimate:

R * C > 2 * t_on

With R and C being the component values, and t_on being the time for the supply to reach 2V. As an example, if your supply takes 1ms to reach 2V, then an RC value of 2ms would be sufficient (0.1uF + 20kΩ).

I would expect a 10kΩ resistor + 0.1uF capacitor to work in most systems.