Your words are clear. It seems difficult to have general rules that apply to all systems. Therefore, I should possibly test a V3 Ethernet cable before installing my switch.
I have a Cisco Meraki MS220 Ethernet switch that has been modified (new clock and disassembly of the entire power supply) by a craftsman named Wattcat located in France who does remarkable work. I have a very high-quality linear power supply, also made by Wattcat, to power my switch.
For more details on Wattcat :
https://forum-hifi.fr/thread-24947-page-15.html
https://www.facebook.com/p/Watt-Cat-100077524891481/
Kind regards
Christophe.