Several plugins and extensions are shown multiple times and others are greyed out and some have version numbers shown as 0.0.0. What should I do about them?
So as to not invite a headache I wouldn't delete any of them, just leave 'em be.
If feeling adventurous I'd disable the questionable ones, and if something hiccups just re-enable them.
Check the PRODUCT column. For me several plugins appear with the same name, but I have both Firefox and Seamonkey installed. The product column will tell you what application they apply to.