Re: UEFI: Need to dual boot Mint on Asus G75 from 2012
Fast Startup/Fast Boot is a Windows 8/8.1/10 feature. The on/off button is hidden in the power settings dialog.
Secure Boot is a toggle in the machine's UEFI settings. Some (e.g. HP) let you simply turn it off. Others, like Acer, require you to set a password first.
Both options can be disabled without taking out the existing Windows installation.
On Debian at least, Grub installs properly using the defaults suggested by the OS installer.