Hi @Buster Dogg,
I have an Helios4 from batch 2 with 4 SATA HDD which are all used by a RAID6 array. The RAID6 device is then encrypted using Luks. And the encrypted device is formatted using btrfs. I don't use OMV because it requires a Debian system, and I use ArchLinux on my Helios4. So all services are manually configured, including Samba. I didn't notice any issue to read large files through Samba shares from other devices (including a Raspberry Pi 3B+). Also no problem of drives unmounting during high load of the system, but I do not have a high system load usually.