1.) The blog post thumbnails with information on hover is the Post Carousel as stated on the previous reply.
1.) Are you referring to the picture above the navigation with headline Let's build your income? When I checked the site, it is built using Pro header builder. Bar with background image, headline and button element.
2.) Those are blog carousel. Make sure to enable a post to display on blog carousel. You can see Post Slider Display – Blog under Ethos Post settings. If you enable that option, that specific blog post will appear on the blog slider under the navigation.
Regarding the error on the customizer, please share your site URL and credentials on a secure note so we can check. It is a good practice to check for plugin conflict too. You can do this by deactivating all third party plugins, and seeing if the problem remains. If it's fixed, you'll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
Blog article navigation is automatic on Ethos stack. We can check after we have check your site blog article. Is that what you are asking the blog article navigation? Or are you asking for the fixed top option of the header? You can set that option on X > Launch > Theme Option > Header > Navbar Position: Choose Fixed Top