Hi,
1) A good host: WPEngine is what we recommend.
2) A plugin cache such as: W3 Total Cache
3) A CDN, we recomend MaxCDN.
4) Optimise your images, before uploading to WordPress. The smush.it plugin will also help reduce image size: https://wordpress.org/plugins/wp-smushit/.
The mobile version of the site is altered by using media queries, these change the layout depending on the screen size or device.
If you wanted to customise the layout, you would need to hire a web developer to assist you.
Thanks,
David.