What is stored in the webserver? (Separated Database)

The WP database contains everything that is related to content: posts, pages, theme settings, plugin settings, media of all kinds. So if you were to replace the WP database with a brand-new WP database, all of your content – and many of your settings – will be gone.

The WP ‘code’ (PHP, CSS, JS source files) is stored in the wp-xxxxx folders, plus the site root. Some CSS might be stored in the WP database, but the ‘core’ code is in the site root and the wp-xxxxx folders.

Can’t speak to load balancing…perhaps someone else will chime in on that.