The best version of OSX for the clamshell is 10.3.9 for speed and overall usability. If you want newer versions of software (like Safari 4) then you'll need to run 10.4 on it. I don't know about the 466MHz models (they may actually be just fine), but my 366MHz indigo is REALLLY slow under 10.4 with 576MB of RAM installed. If you've got less than 320MB of RAM, then I would not recommend running OSX at all. For the other software you mention.

Microsoft Office 2001 is awesome and uses hardly any CPU or RAM compared to the OSX versions.

AppleWorks 6.1

iWork 06 (only if you're running X obviously)