Our default policy is that CC keeps toggle for Rp and Rd. Which means if you connect two CCG3PA power bank, it depends on the timing of connecting two power bank to decide which one is the power source. A good strategy for a power bank is to switch it default power role according to its remaining battery power, which can be done in the firmware.
For your second question, most of the laptop would provide 5V to power bank. Because the laptop would provide power to device connected to its USB port by default.