Should we just either rclone or rsync?

Not if you care about optimizing cost and performance. Single-tool approaches sacrifice either speed (rsync all the way) or efficiency (rclone all the way). Sophisticated teams use both in complementary roles—rclone for bulk transfers, rsync for incremental efficiency.

What about cloud costs? Rclone transfers cost extra bandwidth.

True for egress charges. But if you're doing initial seeding, the time savings often justifies bandwidth cost. For ongoing sync, switch to rsync's delta efficiency. For cloud-to-cloud transfers within the same provider's network, rclone is often the right choice.

Do we need immutable storage for backups?

Ask yourself: "If ransomware compromises our backup system, can the backups still be deleted?" If yes, you have a single point of failure. Immutable storage provides defense-in-depth—even if backup tools are compromised, recovery points survive.

What about commercial backup software vs. these command-line tools?

Commercial software adds value through automation, orchestration, application-aware backup, and disaster recovery testing. But for file-level sync, rclone/rsync are often faster and more flexible. Many organizations use a hybrid approach: command-line tools for data movement, commercial software for orchestration and reporting.

How do we know if our storage is the bottleneck?

Run rclone with --transfers 8, then with --transfers 64. If performance doesn't improve significantly, storage or network is likely the limiting factor. High-performance storage should show near-linear scaling up to network capacity limits.