So according to the Microsoft Docs, ReFS can't be the bootable filesystem on the partition.
does it mean that if I put the boot manager (Windows boot manger or Grub) on a small (<1GB) NTFS partition and then install Windows 10 on a ReFS partition (without boot manager), it will work?
Most likely not.
Windows uses the terms "system" and "boot" in opposite compared to Linux – the system partition is where BOOTMGR lives, and the boot partition is where Windows itself is kept. If the documentation says ReFS is not bootable, it means you cannot put Windows on ReFS.
One job of a bootloader is to load the kernel – just as GRUB needs to understand filesystems (and LVM, and ZFS…) enough to find and read your 'vmlinuz' and 'initramfs' files, the Windows BOOTMGR likewise needs to be able to find and read Winload.efi, NTOSKRNL.EXE, and other related things. It does not know how to do that from ReFS.
(There may be various other reasons why Microsoft did not add this feature, possibly even something that only becomes obvious after they tried and failed, but this is the most basic one.)
A more interesting way to completely break your system might be to install Windows on Btrfs instead, using the WinBtrfs driver and Quibble as a bootloader to match it.
From: here
Since Windows 10 build 20185, Windows bootloader could read from refs, and some Chinese did succeed in booting it via multiple times DISM capture to different fs (including exfat).
so it is quite hacky.
