The issues you describe are related to the FU1 version of the French OS Update 2.0. This version of the update has been available from the Apple Canada Web Site for about 6 months. The FU2 version will take care of most of the issues related to sound on Macintosh Performa and Power Macintosh computers. The only issues not addressed are modem sounds. These are more related to localized versions of the drivers supplied by Global Village and are under investigation by Apple Engineering and Global Village.
Unfortunately, the Mise A Jour FU1 -7.5.3 CD-ROM is the version currently shipping from Claris Canada. The FU2 version is available from Apple Canada's Web Site as well as from SOFTWARE Updates site in the US.