It would be great if you could give us more context as it is difficult to guess.
"Plano largo" sounds to me like a literal translation of "long shot", but I wouldn't use it in Spanish unless I am very influenced by English.
(I'd actually say "un plano telephoto" if using the jargon, which is also a mix of English and Spanish)
"Y lo hace con las decisiones estilísticas que tal empeño merece: planos largos, contención melodramática y austeridad formal."
What I'm afraid is that is means a long duration and not a camera position (i.e. a long shot). There are planos medios, plano secuencia (sequence shot which can be quite long), primer plano u acercamiento (close-up shot) and plano detalle (extreme close-up).
It's a tricky one but my instinct has me agreeing with you, I think they are referring to the duration of the shot, as the other features (contención melodramática y austeridad formal) have more to do with the emotion than with the type of lense they are placing on the camera or its position in regards to the subject.