HI @Espacebleu and thanks for your purcxhase
How can I add these two projects to the list of available projects in the Elements app?
Also, how do future updates for these projects work? Are they handled automatically through the Elements app?
No, the store is not yet available for developers.
In any case, all projects within the integrated store, even if updated, will have no effect on your work. If a project has a bug, you won’t be able to fix it with an update. This applies to all future projects of any kind and from any developer. This must be clear, and thank you for giving me the opportunity to explain it to @everyone.
The only product that updates projects automatically (even fixing bugs) is the component (exactly as happens in stacks with the app’s internal update system). The modularity and automatic theme updates that occurred with RW Classic do not exist in Elements.
The advantage of having element packages and projects in the internal archive is very useful ( also if you change computer and you don’t have a backup)
The real revolution of the archive will be providing updated components and being able to preview them before the purchase!. This is after all the advantages, and RMS is doing an excellent job of this and I’ll also add products in future 
BTW: I recommend always making backups of your work with projects because that is the most important thing for you, and you must do them manually using progressive copies in the cloud.
another detailed reply here
The quality (and longevity) of your work depends on how professional the developer is, beyond the quality of the distribution. I have been supporting customers for 20 years. 
The positive side of elements is that it connects developers more intimately with customers, so to fix a bug in a project or element package, the developer must explain “step by step” to the customer how to resolve the bug in working projects and the CLOUD provided by RMS is the best tool to do it (allows you to exchange large files and maintain mass privacyl between user and the developer) . If you need assistance let me know