By default, it is set to MAXP CORE ARM.

In Jetpack 4.2.1
Power mode on the UI (MAXN, MAXQ, …, …)
What file is saved in this setting?
I’ll ask you for it during the process of creating “rootfs” instead of the UI.

By default, it is set to MAXP CORE ARM.

Not sure for JP4.2.1, but in previous releases you would edit file /etc/nvpmodel.conf and at the end check for

< PM_CONFIG DEFAULT=3 >

that uses by default POWER_MODEL with ID 3 in this example.