Upvote:2
I just did some digging around Brazilian Foreign Affairs and Justice ministries websites and it seems there is no standard answer to both your questions since Every Brazilian Consulate has its own workflow. For any questions, please contact the Brazilian Consulate where your Visa Application will be processed.
I also could not find anything saying you should (or not) apply for Digital Nomad Visa in a 3rd country. It's only stated that there are different procedures if you apply from within Brazil or from outside it (from your own link).
If you really intend to apply from Argentina, you should take a look at their webpage (in spanish) and check which consular representation you should use, based on your current location in Argentina.
You could also check this official social media accounts for consular services around the world (only in Portuguese, but it's just a map) and contact the one you intend to use to obtain your Digital Nomad Visa.
Hope you succeed your visa application and have a nice time in Brazil!