Hi @gerassimos_pari,
As for your questions:
1. That will depend on the application that you are running on the device, you can take a look at the hardware design guide chapter 3.10 Power connectivity/routing. Also please see it on the datasheet chapter 4.1.5 Maximum Supply Currents.
2. The peak current you can look at the datasheet from the PMIC that we use for the i.MX8QM, please refer to the datasheet.
https://www.nxp.com/docs/en/data-sheet/PF8100_PF8200.pdf
3. We do not have an estimated rise time for this, sorry if this may cause you a problem.
Please take a look on the application note that we have for the PMIC, it may help you:
https://www.nxp.com/docs/en/application-note/AN12286.pdf
Regards,
Israel.