Perhaps a bit pedantic, but would be more accurate to say that Base64 encodes binary data into a subset of ASCII characters, since ASCII has 128 code points - 95 printable characters and 33 control characters - whereas Base64 uses 64 - 65 if we include the padding - of those.
In general you want to reduce the amount of things you have to retrieve from memory in one go, and attempting to retrieve a 20 person list is just going to give you problems.
The cloze solution is certainly better than the full list (and does follow the minimum information principle because you just have to retrieve a single name) but the problem is that it doesn't give you any handles. If you have 19 names and Flaubert is hidden, how would you know it's Flaubert that's missing? Long-term you're bound to fail those cards.
But I would also question the premise of the card. Do you expect to have to come up with the 20 names each time you want to talk about 19th century French literature? As in, each time the context is "19th century French literature" is the appropriate knowledge to retrieve "* list of 20 authors *"?
Instead a better approach might be to flip it around and ask yourself, "In which century did Flaubert write Madame Bovary?" or something along those lines. You can both reconstruct the list from that and if you're writing about Flaubert the knowledge that he wrote during the 19th century will come more fluidly to you.
My number one recommendation is to not get overly excited about it. One of the first things that happen when you start using Anki and realize the superpower that it is being in charge of your memory is that you want to include EVERYTHING in it.
You start creating cards with obscure bash one-liners, little-used git commands, or Javascript functions you read about in a random article. You add all of it to Anki. After all, you might use them in the future right? And it doesn't cost you anything to create a card with them so why not.
What happens is that because you don't have a clear picture of why those cards are valuable to you - you just added them because they might be useful, one of these days - you will have trouble retaining their knowledge, meaning that you will keep failing to successfully review those cards.
And because of the way spaced repetition algorithms work, those cards will be constantly appearing in your reviews, and you will keep failing them. And they will keep appearing. And so on and so forth until you lose all motivation to use Anki because it's becoming a frustrating experience to do your reviews.
The most important thing about using Anki is to keep using it. That's how you get the benefits of it, so be more selective about what you add to Anki instead of profligately adding cards that you gain nothing from.