It seems like you are planning to find a rechargeable battery solution for Jetson Nano Developer Kit (B01).
In the end, you would need to test some battery solutions in your particular setup and see if they satisfy all the requirements, but I can share some of my thoughts.
First, you want to estimate the max and average current consumption of your whole system.
On top of Jetson Nano Developer Kit itself, you also need to factor in your 2 of USB 3.0 devices.
Then, you want to check both the max current output capability and the power capacity of your battery solution.
As to the max current;
If you assume the whole system to consume 4A@5V (Jetson Nano module + 2x USB 3.0 devices and others), your battery solution needs to be able to supply 4A at 5V.
You definitely need to make sure the spec of the battery solution shows that it can output whatever the amp you need at 5V.
Depending on your current requirement, you may need to look at a higher voltage battery and use a step-down converter to bring down to 5V so that the battery solution can output enough current.
And some battery solutions (especially USB power bank) may not be able to output its maximum current (A) at high enough voltage for Jetson Nano, so you need to actually test your battery solution.
As to the power capacity calculation, it may go like this;
If you assume the whole system to consume 4A@5V (Jetson Nano module + 2x USB 3.0 devices and others), running for 2 hours requires 40Wh (5V * 4A * 2h).
If you are planning to use a USB power bank, you will see some advertising like “10000mAh”. Such power bank often measures the capacity as if it has 1 cell, so the capacity of the battery is calculated as 37Wh (10000mAh x 3.7V).
Of course, this is all theoretical. You may need to factor efficiencies of all the converters.
Lastly, it is best to supply power through either DC power jack or 5V pins on 40pin header.
MicroUSB might not accommodate the current required depending on your actual application.