The domain masking that Nayeli is doing in her YouTube video is only really recommended for the one page, however there is nothing stopping you trying it with more pages and see how well it works.
Just note that Wix will not allow you to do it, so it will always have to be through an outside provider like 1&1 that Nayeli used in the tutorial or another provider like GoDaddy for example.
To do it through Wix you would only really have the router option open to you.
This has been asked before as well.
https://www.wix.com/corvid/forum/community-discussion/url-domain-masking
Also, note that there are many pros and cons online about doing this…
DOMAIN NAME CLOAKING & MASKING
Cloaking and masking mean the same thing. Using this method, your web pages will appear in a browser “frame” while the browser address bar will show your domain name. No matter what page is visited on your web site, the address won’t change when using masking.
Cloaking/masking isn’t an ideal use of your domain name as your visitors won’t be able to bookmark specific pages and search engines are more likely to list your pages under the server on which they are hosted; rather than under your domain name.
What is URL masking?
URL masking, also known as cloaked URL forwarding, or link cloaking, uses your domain name for your website in a different way. In this case, the domain points to a browser with a frame which shows your website within it. No matter which page you click on your website, the URL in your address bar stays the same. Your URL is cloaking or masking the real address of your website, which is the server that they are hosted on.
For example, if your URL is www.MyWebsite.com, and a user clicks away from your homepage to another page (such as your contact page), this does not change in your address bar. On a website with a properly hosted domain, the URL in your address bar would change with each page visited. So the contact page on your website would show as mywebsite.com is available for purchase - Sedo.com. Cloaked URLs are common with free web hosts, which let users build a site and select domains that are only pointed to pages with the frames mentioned above.
A great metaphor when describing the difference between URL redirection and cloaked URL forwarding: “Cloaking and forwarding are a little like a redirection service you put on your mail when moving to a new house; whereas using name servers is the actual address of your new premises.”
The dangers of URL masking: for site owners and site users
Having a masked URL poses issues for several reasons. First, site visitors are not able to see the direct addresses of the pages that they are visiting on a webpage, which means they are not able to bookmark or share specific sections of a website. If you have content that you would like your users to share and link back to, they are unable to because they do not have the actual URL for each page of your website.
Cloaked URLs also have negative effects on a website’s search engine rankings. Because websites with masked URLs are hosted on servers with entirely different addresses, search engines will crawl them on those servers, rather than the domain that website owners or managers want them to be crawled on. Search engines are actively punishing websites with cloaked URLs because they are flagged for duplicate content. If you have two different sites serving exactly the same content (which is what it will look like if you’re using URL masking), then which one is authoritative? Which one is correct? Google will penalize sites with duplicate content. This does not happen when a permanent 301 redirect is used, because search engines know to look at the destination of the redirect.
For users, cloaked URLs also pose a security threat. URL masking can be used to create malicious websites that hide their real addresses from the users for nefarious purposes such as phishing or malware deployment. Even if a website owner has good intentions for using URL masking, it can also be prevented from working properly. It is also used for a practice called clickjacking , which has also been used to trick users into performing actions such as adding likes on social media sites or adding clicks on ads, none of which the user intended to do.