Does a UK citizen need a visa to travel to and from the EU after Brexit?

I'm a UK citizen and am about to move to the EU (Austria, specifically). Since the Brexit transition period lasts until the end of the 2020, I can travel without a visa for now, and my current understanding is that I can stay in the EU after Brexit without applying for a visa, the same as if I had moved a year ago (source).

However, suppose that I travel back to the UK for a few days, via a different Schengen area country (e.g. France/Belgium/Netherlands), either during/after the ending of the transition period. Will my Austrian "e-card" and residency permit be sufficient to re-enter the other Schengen country from the UK, or as a non-EU-citizen, must I apply for a visa to do this?

Edit:

As explained in another question, I did not manage to get the paperwork completed before the end of 2020. I am unsure whether this changes anything, or of what document, precisely, is required. As far as I can tell, there are 3 "levels" of residency document:

• the "Meldezettel" (registration of my apartment with the local authority, required for all Austrians and foreigners). I have this.
• the "Residency certificate" which proves that I was resident in the country before 2021. The Meldezettel is a prerequisite for this along with various other documents. I hope to have this soon.
• the "Article 50 Residence card", for which a "Residency certificate" is a prerequisite, which I can start applying for in 2021. I have no idea how long this will take.

Assuming that foreign travel becomes safe, which of these would be sufficient to re-enter the Schengen area from the UK without a visa? What about for travelling within the Schengen area but not leaving it?