A Wix site can't leave Wix, and the Wix help center says so in so many words. Your site is built with Wix's technology and, to work properly, it needs to be hosted and operated on Wix's servers. You can connect a domain bought elsewhere, which I recommend in my guide to domain names, but the pages and the layout stay inside the editor. The day you want to leave, you copy your texts and images by hand and rebuild everything else. That's the Wix business model, and you should know it before you build ten years of trade on top of it.
A template that anyone can pick is used by many other sites, and nothing stops a competitor in your town from starting with the same one. The structure fixes the order of the blocks and the height of the banner, and your texts go into boxes designed for a generic business. You can change everything, the Wix page says so, but every change takes time and often breaks the layout on phones. A site coded for your business starts from your services and your customers, and no two of my clients get the same site.
Page speed depends on what the page carries. A site built inside an online editor loads the editor's code, the scripts shared by every site on the platform and each app added from the app market before your first heading appears. Wix says it serves pages from servers close to your visitors, which helps delivery but doesn't reduce what the phone then has to read and run. A site coded for you contains only what your pages need. Before going live, every site I deliver passes a check on speed, accessibility and technical SEO, and I show you the results rather than promise them.
The full cost of a Wix site is the subscription plus your hours. The Core plan at $29 a month comes to $1044 over three years at the displayed price, before paid apps and before the time you spend in the editor each time a page has to change. My Essential plan costs €1,405 over the same period, and that amount covers design, code, hosting, backups, updates and your changes delivered within 48 working hours. On subscription alone Wix stays cheaper, and the difference pays for the work you no longer do. If your time has a value for your business, run the numbers with your hourly rate and read what a cheap website really costs.