Hello, you are welcome :)
1) Wintoolkit correctly import all registry keys, even those TrustedInstaller ones, i verified that since the beginning :)
i don't really know how the developer accomplish that
2) I only started creating LP addons since 4.7.1 due requests, indeed, they are not very useful except to silence Windows Update
3) I don't know for sure, but i tend to leave configurations as default like original setup, the user can disable it then
regarding integration, i actually have mini pack for personal use, which extract/prepare/integrate the addon without Wintoolkit :)
i use NSudo to get TrustedInstaller rights