Hello,
for a better performance I'd like to install an optimizer plugin. Is this recommended or not? Which css and js shoul I better exclude?
I have standard template.

And still another question: Is there anything to update (template, framework, etc...)

Hi
optimizer..there is so many variables in Joomla that only way to find out is actually try it.

As fo updates....follow our updates stream or twitter where you can see updated extensions.