I just tried copying a large video file onto the NAS via smb and get around 700MB/s, which is around what I would expect for the setup (5 * 16TB ironwolf pro in raid5, connected via thunderbolt to an sfp+ adapter). Few other things you could try apart from those articles:
* `defaults write com.apple.desktopservices DSDontWriteNetworkStores -bool TRUE` to not write the DS files to network locations
* Connect via IP address in cmd+K connect window.
* _Turn off_ wifi completely when you connect via ethernet. Otherwise it's very likely the connection will still end up going through the wifi interface.
* Enable jumbo frames on the interface (mtu 9000).
* Check `smbutil statshares -a`. You want SMB 3. If it's a LAN and you don't care about encryption, then `SMB_CURR_ENCRYPT_ALGORITHM` should be `off`.
1. https://support.apple.com/en-us/102010
2. https://support.apple.com/en-us/102050
3. https://wiki.samba.org/index.php/Configure_Samba_to_Work_Bet...