So I can power the arduino nano with a power bank via the micro usb port? That sounds great, lot less complicated than using the Vin pin. Not that it's not very complicated to begin with!

Yes, you can. It is the easiest way to get battery power but not very compact. When the time comes to fit things into a smaller package, you can look at other solutions.

 

To add to the noise,
I think the nano uses a LDO for power regulation, so will not be kind with a higher voltage battery and its charge life,

this could be an interesting thread

https://forum.arduino.cc/index.php?topic=671458.0

 

To add to the noise,
I think the nano uses a LDO for power regulation, so will not be kind with a higher voltage battery and its charge life,

this could be an interesting thread

https://forum.arduino.cc/index.php?topic=671458.0

lot of the 9V battery will be eaten up as heat in the linear regulator. That's one thing that makes it worse.