I am dual booting with windows and i have some doubts

hei @rocksj long time no see…

  • as long as you want to be able to boot EnderavourOS secure boot needs to be off.
  • the option is not added to the Bios/Firmware it is a kernel boot option added while booting the Linux Kernel.
    To have it permanently added you need to add it to grub configuration:
    Nvidia driver problems - #11 by joekamprad

You will need to remove the nvram boot entry and set it to use the Windows ESP again.
Depending on how you setup.
Updating Windows should not harm… but there are cases where it happens that windows were changing/deleting stuff so nothing someone would give a guarantee on here.
The only suggestion: BAckups BackUps BackupS …