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Yes the FlashFXP backup file .fbk restores/backups everything including sites and passwords in said sites, bookmars and everything the version of flashfxp backup supported/contained, including program prefs, afaik I dont think it can import sites from ftprush.
Below is all the supported sites and whatever formats they use, so it may pay if the FlashFXP restore doesnt have all the sites you need, to adjust the format of your xml or text a bit to compensate.
though that does mean you need to mess with the file layouts
