I went to that site & scrounged around for a page that contained free content. I'm not entirely sure if there's a paywall involved here. The site offered to take me to their US site but I stayed on the Oz site. I went to this page:
https://www.clickview.com.au/free-teaching-resources/I picked the first video & got it to play. Things looked like this:
There were many variants on the VDH menu, all named the exact same thing, which isn't very helpful. I decided to pick the one at the bottom of the VDH menu. It turned out not to be the one you can see playing in the image above. It downloaded in about 2 minutes & played just fine in VLC, although I just sampled it at intervals to make sure both video & audio were there. After I saw that I had a video that wasn't the one I had tried to play on the web page, I looked more closely at the page. It seems those videos are in a long ribbon. Unrolling the ribbon to the right, I discovered that I had downloaded the last video:

It appears that these videos actually play on this page. Clicking one of the thumbnails launches the video. It does not take you to a new page. Since the videos are all on this one page, VDH recognized them all. By going to the bottom of the VDH menu, I had done the equivalent of unrolling the ribbon to the end. I didn't know that up front. I guess the variant for the video actually playing in my first image above is the first variant on the VDH menu. It is annoying that VDH doesn't give you different names for each video but that's not news. This is the situation on a lot of web sites.
I don't know if this really answers the question here. If there is a paywall involved, it may not work like this. These do seem to be small sample videos. At least they worked for me in the US even though I stayed on the Oz site.
As for the watermark, yes, purchasing a license will avoid writing the watermark when you download content from here. However, I would test whether VDH is able to get the content you're interested in before you buy a license. I assume these free samples are not what you are really interested in. So test it on real content before you buy. You can always buy a license & redownload whatever you got as a test in order to not have the watermark.
I am including images in this post. When you do a Reply all here, as you will to respond to this post, you will duplicate those images in your post, a useless & wasteful occurrence, if you don't take the appropriate measures to prevent that. The appropriate measures are documented over here:
https://groups.google.com/g/video-downloadhelper-q-and-a/c/BzPLK2YyL-sSearch for "stealth quote" within the text of that page. That will reposition the page to a reference containing a link. Click that link & be sure you follow the advice you will find when you next post here.