Wait till you learn about Wireguard.

Sure, but why not webUI vs VDI?

Funny idea but I see no point in it?

Use XFS as file system and use --reflink when you copy the volumes, creates an instant CoW copy no matter how big the folder is. You can then move, copy or whatever that folder to anywhere, or use a VM and simply backup the VM.

Just use Plex offline and you are good to go. If you don't know how to use Plex offline read up about reverse proxies like Nginx and how you can allow access to download meta data but block basically all the rest and even fake that Plex thinks its online.

I think we can all agree that a CPU from 2007 which does not support VT-x is not a good pick even for something that is just meant for education.

Every webcam provides an RTSP stream already and most have a webui with the live stream or do you mean to stream via a website publicliy available on the web?

sshfs-win is something if you don't like vscode.

Check your routing. You probably forgot to push the routes of your security camera subnet to your client config.

SMB.

Transmission and then your normal *arr stack.

A simple webserver secured by htaccess is not inherit insecure, but there are a lot of steps you can take to improve security further: Like proper authentication via OICD or something similar. Only access to the server via VPN, files encrypted, and so on.