Just to follow up, here's a sample of normal backups followed by a Cloudron upgrade, which itself triggered another backup run, and the corresponding relevant network and disk graphs:
Network Traffic.png Disk I_O.png
All in all, it's definitely fast-er but not insanely performant. CPU utilization vs load hints that it may in fact be down to inefficient utilization of cores to some extent, but there is definitely a fair bit more bottleneck coming from the network still.
CPU Utilization.png CPU Load.png
Nothing earth-shattering either way, and gains were more mild than I would have guessed, but all in all, not a bad outcome.