I know there are a couple of different Daggerfall versions out there. I believe one is DaggerfallXL or something like that. Can someone explain to me which one this is? Is it complete? And does it work via DosBox?

The GOG version is the latest official version of Daggerfall (released as freeware by Bethesda) integrated with DOSBox.
For more information regarding Daggerfall see [url=https://en.uesp.net/wiki/Daggerfall:Daggerfall]https://en.uesp.net/wiki/Daggerfall:Daggerfall[/url].

Thanks!

It's not a source port, and as far as I know, it contains no community content. (Haven't tried their version, though.)
As always, I'd recommend instead trying this version, which, while it still just uses DOSBox, at least comes with a bunch of optional community-created components that you can enable at installation.

Fixed. Thanks for telling me. :) I replaced the colon in the URL (which is what made your first link not work right, BTW; in your subsequent link, there's also a number sign/"hashtag" that's causing problems) with what I thought was its HTML character code, but I was working by memory, and used the code for the wrong character. :P Not sure why you mentioned all the additional content, then linked to a section almost all the way at the end of the page, thus skipping the descriptions of most of the content (and their aforementioned links) ;P All the same, I fixed your link in my reply quote above.

Your link works now. DaggerfallSetup is a great bundle of Daggerfall and user-made content indeed. The underlying Daggerfall version is exactly the same as the one GOG uses, but I haven't checked the two DOSBox frontends for tangible differences.
For people who are interested in playing Daggerfall and are not interested in GOG (who don't offer a separate download of Daggerfall anyway, to my knowledge), DaggerfallSetup is highly recommendable. If someone feels overwhelmed by the many different additions to Daggerfall, he/she should simply install the base game, nothing else, and worry about additional stuff later.

The way the URL's are shown in my post is GOG's formatting - I simply copy the URL's from my browser and paste them into my post. Only when I save the post, this odd formatting is applied. In my other posts the URL's are presented in the normal way - don't know why this post is different. Nevertheless, my URL's are correct (at least they lead to the correct page when I highlight them in the post and select "open link").
I wasn't aware that my second link leads to the end of the corresponding UESP section :-). I glanced over the section in my browser and copied the URL when I had reached the bottom. Apparently this didn't only include the URL itself but also the screen or cursor position - interesting! Thanks for making me aware!

To be absolutely clear, you can do that in the installer -- all you have to do is tick the various checkboxes. Something in GOG's forum code was broken a couple years ago so that it no longer accepts certain "special" characters in links outside of specific contexts. The "#" in your link (which most wikis and some other websites do indeed use for links to a certain position within a page, as in this case) is such a character, as is the second ":" in both our links (it allows the colon between the initial "http[s]" and the "//" in URLs, of course -- otherwise, no links would work ;D ). The workaround is to instead use the HTML character replacement codes (from a list such as this) within the URL tags.

Good to know - thanks!