Notepad was just a wrapper around some default win32 controls. Judging alone by exe size is not right, although probably a “statically linked” notepad would still be smaller than emacs
It is a flag that says whether the loader data is initialized or not.
The layout of PEB_LDR_DATA “leaked” long time ago in public PDBs.
More context: It has nothing to do with debugging. However, if you attach to the process early enough, you might see the flag as 0 and eventually it would switch to 1. That is probably what threw him off.
The repositories shown on the first page of GitHub search are not actual exploits. They all expect to be run through an admin powershell/command line. Under normal conditions (default user and UAC on) you will get a warning before the script is able to gain administrative access. Try to run them again under a normal user and they won't be able to disable/bypass Defender.
It's the same as sudo'ing an unknown script you received in an email. At that point you're begging to be pwned.