Hi!
1. Make sure the search override feature is enabled. This should work with every theme, which follows the basic coding guidelines. In case it does not, then check this configuration as well.
2. Unfortunately there is no such feature built-in within the plugin. I usually recommend using a pop-up feature of a page builder like Elementor, Visual Composer or similar – where you can place the plugin shortcode. Most themes nowadays are also equipped with some page builder features including a pop-up, there might be one included with yours as well.