I’ll just explain what they mean and you can judge when each is appropriate.
Install in MBR means you are taking control of the boot first thing. So this GRUB can boot openSUSE, and other OSes. If you already have Windows, this overwrites the Windows MBR.
Install in root partition expects the first bootloader to chain to it. The first bootloader could be GRUB or Windows.
None means you have to arrange for some other bootloader to load openSUSE. For instance you already have GRUB from Ubuntu in the MBR and you just add an entry for openSUSE.
I always use the MBR. But often by default if suse is left to install on a win machine - shrinking win partition etc… it will not place it on MBR, but boot from root with grub and active flag on the extended.