Setting up second QNAP only for backup

[janwer]

Primary TVS-951x. RAID5 5x3TB HGST for media, photos, Plex, Roon. RAID1 2x0,5TB SSD for system and databases. Snapshots.
Secondary TS-431P2. RAID5 4x3TB HGST only daily backup with HBS3 and maybe snapshots from primary.

Is there any sense to have snapshots on secondary backup QNAP? If no should i make thick or static volume? Use 100% available pool space or less?
Which is better snapshot replication or storage?
What is the use of snapshots if I'll have daily versioned backup?