A typical uninstall of NVDA (like a lot of programs) does not remove user settings by default. I have uninstalled and reinstalled on multiple occasions and all of my user settings and add-ons have remained entirely intact (with the exception, of course, of certain incompatible add-ons being disabled if the newer version of NVDA determines them to be incompatible. But that doesn't count, as it's by design, and the add-ons aren't removed, they're still shown in add-ons manager and disabled).
If someone wants to create a portable version of the current instance of NVDA with all settings, then more power to them. But it's generally unnecessary.
Most modern programs employ the individual user account's AppData directory (which is normally an invisible folder in Windows unless you tweak things to make it show) to store things like settings and the like that are user selected, and uninstalls almost never remove these by default, though many give the option of removing them if you don't intend to reinstall, and the dialogs related to the removal make that very clear.
Brian - Windows 10, 64-Bit, Version 21H2, Build 19044
The instinctive need to be the member of a closely-knit group fighting for common ideals may grow so strong that it becomes inessential what these ideals are.
~ Konrad Lorenz (1903-1989)