I don’t exactly get what you are looking for. It may be the case NC15 ist faster then NC21. I assume current version has contains move moving parts.
My test show that NC itself and traefik CAN saturate the network - see another test, here I added 4 files with total size of 3,5GB. It was interesting initially I had send speed close to 1 GBit/s, then short pause and then another block at ~300-500MBit/s. complete transfer was finished in less then 40 seconds on NC21 container with traefik, with HTTPS
Downloading this 4 files (uploaded via Web) happens in two chunks with >500Mbit/s speed, again complete 3,5GB is received in less then a minute.
definitely if you calculate an average network load it would be far less then real transfer speed. Additionally all the tests show similar behavior - a transfer starts much faster and settles at lower rate later - most likely there is some caching which saturates after 1-2GB and falls back to the bare-metal limits (in my case most likely spinning disk)
My earlier statement regarding syncing small files is slower doesn’t meant overhead as “additional network traffic” but everything inside the system, adding new files to DB, updating indices and so on. I don’t have a proof but I would expect the system is busy doing some things in background an just doesn’t use the network at this time - this is the reason huge files sync lot faster as small files because such overhead is almost constant per file an doesn’t really matter if you sync iso files or movies but hurts if you upload thousands of small text files.
your system may have some bottleneck but I conclude with my tests NC21 itself and traefik don’t apply this limits if the hardware performs well. New versions consume more resources then older versions - and offer you more functionality. You may try to remove apps you don’t need like activity, deck, unified search - maybe this results in a speed improvement which satisfy you needs.