Hey there,
Thanks for posting. With the plugin update, we made some changes to the CSS with the intention that it would inherit and integrate with existing site stylesheets a bit better than before, so I’m sorry to hear that you’re seeing some unwanted changes come along with the new version.
The plugin settings do offer the ability to enable and disable a few custom styling options, though it doesn’t include all of the CSS that come along with the plugin (specifically the code you mentioned in the mailchimp_widget.php file), so it’s possible that disabling custom styling in the plugin settings may not address the issues that you’re seeing.
On my end, I’ll make sure to pass along a feature request to include the option of disabling all CSS included with the plugin.
In the mean time, the best bet to fully disable the style code would be to remove the CSS code from the file that you referenced. Alternatively, I’d be happy to take a look at your site to see if there’s any suggestions I can make as far as adding some custom CSS to help address the issues that you’re seeing. In this case, if you’d like to post a link to your site (or email me directly at mailchimptk[at]gmail.com) I’d be happy to help!
-tk
