You should show Google what an end-user would see.
Check the Google Webmaster Guidelines
Make pages primarily for users, not for search engines.
Don't deceive your users.
Avoid tricks intended to improve search engine rankings. A good rule of thumb is whether you'd feel comfortable explaining what you've done to a website ...
Google reads CSS so in short. Yes. The overall page will be rendered by Google and used to determine if mobile friendly etc. If you aren't serving media queries in your CSS that will be a problem. Theres lots of best practice reading around that. E.g this page exists for a reason.
It's also likely that ...