Check out the Qubes Community Documentation - It covers some topics you may be interested in. Please note that these tutorials are made by Qubes community memebers and not by Qubes.
Also in regards to the ethernet issue, there was a thread posted a few days ago that explains how to fix this in some cases Qualcomm Atheros Killer E220x -no wired network Qubes-kernel 5.10+ - #20 by Cpotts.