What is the overhead of ZFS RAIDz1/2 in HPC SSD Environment?
Use ZFS. Use LZ4 compression. Tune your ZFS appropriately, as defaults won't be ideal for that many NVMe drives.
Test and benchmark with your actual workloads. We can't tell you how it will perform.
RAIDZ overhead is not a concern for this.
The microbenchmarks for the CPU automatically choose the fastest for your given platform.
See the ZFS module parameters:
As BTRFS RAID5 is not considered 100% stable, I do not suggest it even for a backup machine. Moreover, with these large SSDs I would use RAID6 rather than RAID5.
So I suggest using MD RAID6 with XFS or, being an Ubuntu machine, ZFS RAIDZ2 with lz4 compression.
EDIT: I simply do not consider using single-drive BTRFS filesystems as a valid backup approach. In this config, any single drive failure will lead to (partial) data loss. I strongly suggest you to use RAIDZ2 with LZ4 compression or, for maximum performance, MD RAID6 with XFS (but losing compression and checksumming).