I thought I read that if my network connections, both wifi/ethernet, are NOT on, that if someone wanted to try and work on hacking my OS, that they would have to wait until the network connection is active, even if my computer and everything connected to it is powered on (firewall, switch, router, etc).
Of course you disable all your connection noone will be able to access your system but that does not provide you any protection for when you reconnect.
If someone wants to access your system it will simply wait for the connection to be up and then attempt the access.
So you should not count on such a thing as a primary security measure. It's fine to have for when you're not working on your PC, but should not be treated as a solid security measure.
Further, if your system is already infected with something, your network connections could be reconnected automatically by the malware. And if you can physically remove the wire, in the case of wireless, a malware could just re-enable the adapter and connect to your network via wireless.
The network is not the only attack surface for an attacker. An attacker with physical access to your computer, especially if it is powered on, can also gain a lot of information that way.
For example, an attacker can get access to the memory of your computer, which may contain valuable information. If your hard drive or SSD is not encrypted, it can be removed and duplicated, giving an attacker access to all your data.
If the attacker has prolonged access to your system, they may replace certain hardware with their own. This would be incredibly difficult to detect, even if you suspect that this is what is happening.
Rule #3 of the 10 immutable laws of security states:
If a bad guy has unrestricted physical access to your computer, it’s not your computer anymore.