For a good read on WinPE, check out the Microsoft Docs
Windows PE (WinPE)
docsmsft
Winlogon
Winlogon.exe is executed on startup. This will read the WinPE Registry at HKLM\System\Setup for the CmdLine value. By default this is winpeshl.exe. When winpeshl.exe executes, it reads values from winpeshl.ini