The card types do not directly match the OpenGraph ones - if you share an og:article, then Twitter will render a summary card, but not a summary_large_image card, so in that case you'd want to add the twitter:card type tag. However, you're right, in most cases the twitter: tags do map to og: equivalents, so you can keep the amount of markup to a minimum if you use the og: fallbacks in most cases.
The card types do not directly match the OpenGraph ones - if you share an og:article, then Twitter will render a summary card, but not a summary_large_image card, so in that case you'd want to add the twitter:card type tag. However, you're right, in most cases the twitter: tags do map to og: equivalents, so you can keep the amount of markup to a minimum if you use the og: fallbacks in most cases.
Thx a lot for the interesting add-on/answer @andypiper !