Why the word order couldn't be swiched to: "Are these cars brazilian or german?"
Possibly to keep the structure as close to the original as possible.
"Are these cars Brazilian or German?" -- "Ezek az autók brazilok vagy németek?"
Adjectives are not pluralized when they are part of the noun phrase: "brazil autók"/"Brazilian cars"
They are only pluralized when they are linked to the noun with a verb: "az autók németek"/"the cars are German". Yes, here the verb is left out in Hungarian, but I think the difference should be clear.
"Brazilian or German cars"/"brazil vagy német autók" is a single noun phrase (or a contraction of two noun phrases? I'm not a linguist), so there is no pluralization
Aha. Az autók németek = "The cars are German," whereas Az nemet autók = "The German cars?" Got it I think.
Yes, exactly! (Except that it must be "a német autók"; it's always "a" or "az" depending on whether the immediately following word begins with a consonant or not.)