Hey Jeremy, welcome. Great question, but no clear answer! It’s a combination of all those factors, I’d say:
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Sometimes, it’s the spelling that pushes us in a certain direction: we say uma Coca Cola, but um Sumol; uma Fanta, but um Compal. And yet, these are all bebidas (drinks), which is a feminine noun.
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Other times, the implied word is the dominant factor. Among other things, this does apply to vehicles. However, each type of vehicle has its own gender! Carros (cars) and camiões (trucks) are masculine, but motas (motorcycles) and carrinhas (vans) are feminine, for example. So, depending on the context, you might say both “um (carro) Honda” and “uma (mota) Honda”. Similarly, you might say “vou ao (website) Google”, and then later talk about “a (empresa - company) Google”.
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Other times, it’s just not very clear. For example, most people I know (myself included) say “a Netflix”, but “o Spotify”.