In the past I have used Proxmox with ZFS raid on a basic mini PC. With ZFS raid it syncs everything except /boot. Proxmox has a tool called "proxmox-boot-tool-refresh" which will syncs /boot between drives. ZFS kernel module can be loaded in the initramfs so it will boot fine, even if missing a drive.
For this project I do not plan to use ZFS, but AFAIK software raid is now standard. Here is a popular video from Level1Techs talking about the flaws of hardware RAID: https://youtu.be/l55GfAwa8RI