You'll know the installation is successful by signing into the Qualified application to see your live website traffic. It's a good idea to do a quick test by opening an incognito window and testing all of the sections on your website, including your main marketing site. landing pages, blog pages, and pages served by other apps, such as content pages. You'll see the visitors on your site on the main map, as seen below.
The Qualified JS is a 76 kb snippet that fires asynchronously on your website after first contentful paint, so there will be no (or technically a negligible) performance impact to site load time.
The remainder of the loading sequence also happens asynchronously to serve the personalized experience.