Perhaps I am overanalyzing this, most likely. For instance, I want to include my domain on both Dan and Afternic, with the latter hosting my landing page. If I go ahead and put in the TXT Record for Afternic, do I have to wait for verification before changing my Nameservers to Dan?

Once I change to Dan's Nameservers, wouldn't the TXT Records be inaccessible due to Afternic since Dan is now in control of them? As you can see, I tend to overthink things. Any help with clarifying this would be appreciated!

I was able to accomplish this by using Epik registrar, directing it to Epik marketplace NS, and then adding a TXT record to Dan. The only downside was that I got Epik's landing pages. It's possible to do the same thing at SAV, NameCheap, and Porkbun.
Additionally, I heard rumors that Dan intends to become a registrar, which may make it easier to achieve this with them in the near future.

You don't need a TXT record to add names to Afternic; just add the names and they will appear on your portfolio after a brief review. If a name already exists in their database, send them an email with a screenshot from the backend of your registrar where your name appears.

What you're describing applies to listing on Sedo. To start with Sedo, you need to add a TXT record to your current registrar, but it's not related to whether you're using Dan, Epik, Dynadot or any other registrar - this TXT record merely confirms to Sedo that you are the owner of the name. It does not have any additional impact.

Sedo offers a search for alternative options and has been beneficial for several organizations. One example is Techguy.org, who purchased a similar domain name in the com zone to bring in more potential customers. Another example is Bices Florist, who purchased a shorter domain name, bices.com, which increased traffic to their website by 75%. Sedo also offers a Premium Domain Brokerage Program for exclusive sale of high traffic and high-priced domain names. In 2005, this program supported expensive domain name sales, such as Chat.de for $470,000.

Sedo proposed to ICANN to regulate auction sales on the Internet of single-character domains in the com domain, which came amid criticism of ICANN for its proposed increase in the cost of registering domain names in public domains. Sedo's proposal would allow for professional distribution of attractive domain names and use proceeds from sales to compensate for ICANN's growing expenses. The attractiveness of a domain is evaluated based on site parameters such as memorability, brevity, and history, which is valuable for both buyers and sellers.

When you add the TXT record for Afternic, it's used for domain verification. This record serves as a method for Afternic to confirm your ownership of the domain. It's important to note that adding this record does not immediately impact your nameserver settings. The TXT record is a standalone verification mechanism and does not directly affect the DNS resolution or nameserver delegation.

Once the domain ownership is successfully verified with Afternic, you can proceed to set up the landing page on their platform. At this stage, the domain functions as per the existing nameserver configuration, and the TXT record remains in place for Afternic's verification purposes.

Next, when you initiate the process of changing your nameservers to Dan, it's crucial to understand the implications of this action. By changing the nameservers, you are effectively transferring the authority of DNS management to Dan's nameservers. This means that Dan will be responsible for hosting the DNS records, including any existing TXT records.

As you rightly pointed out, the potential challenge arises from ensuring that the TXT records, critical for domain verification and other purposes, remain accessible after the transfer of nameserver control to Dan. This requires clear communication and collaboration with both Afternic and Dan.

Before changing the nameservers to Dan, it's important to reach out to Afternic to ensure that the domain verification process is unaffected by the upcoming change. Afternic may provide guidance on how to manage the domain verification during and after the transfer of nameserver control.

Once the nameserver change is complete and the domain is fully managed by Dan's nameservers, it's essential to work with Dan's technical support or domain management interface to ensure that the required TXT records are correctly configured and accessible on their DNS infrastructure.

Furthermore, it's advisable to maintain open communication with both Afternic and Dan throughout this process. By clearly articulating your requirements and seeking assistance from the technical teams of both platforms, you can navigate the transition smoothly.
The key to a successful integration of your domain with both Afternic and Dan lies in meticulous planning, proactive communication, and technical coordination to ensure that the domain's functionality, including the critical TXT records, remains uninterrupted throughout the transition.