Under the advanced options for a file type what do the following options mean when checked

Replace the current actions for this type of files
Allow modification in the "Folder Options"

I cant find any documentation on the french web site that cover these.

First option: windows has its own file associations, this option tells KFA to overwrite them instead of append
Second option: allow you to see and update file associations as "usual" under windows (Windows Explorer -> Tools -> Folder Options -> File types)