That's the first thing I disable after ever Windows 10 update (it keeps getting reset for some reason). If you have a dual-boot setup, it can result in a corrupted partition if you try to access your Windows 10 partition from another OS when fast start is enabled.
Nope; if the hibernated OS has the storage volume mounted, and you edit that volume in another OS, separate or not you will end up with corruption, just as if two machines had mounted it simultaneously.
