I've never used eZ webin but I think that you can change the look of your site by modifying the <head></head> section of the pagelayout (but there is other solution like creating your own extension design).
For the display of :
extension/ezwebin/design/ezwebin/templates/pagelayout.tpl
extension/ezwebin/design/ezwebin/templates/page_head.tpl
extension/ezwebin/design/ezwebin/templates/link.tpl
extension/ezwebin/design/ezwebin/templates/page_head_style.tpl
extension/ezwebin/design/ezwebin/templates/page_head_script.tpl extension/ezwebin/design/ezwebin/templates/page_header.tpl
It's because the "inline template debug" is activited for your siteaccess.
I have checked "inline template debug" is not activited for our siteaccess (Global override). Still I am getting the templates file paths on all pages of site.
Also, I tried modifying Pagelayout for personalization and it is working fine.
it's a little bit difficult to explain you how to make an extension.
You can read this: http://ez.no/developer/articles/an_introduction_to_developing_ez_publish_extensions
But it's not obligatory to use extension. You can use the override system for creating your own pagelayout and other templates.
I have checked "inline template debug" is not activited for our siteaccess (Global override). Not seeing any template file paths, If I don't clear cache.
Am not able to understand how Cache is working in Ez Publish (4.1.0).