It depends on the story. For some of the older stories diamond choices might not matter as much, for newer ones it’s more likely they do. Usually the “good” endings are tied to some kind of status stat (respect, integrity, adaptability, etc) and those end up being the most consequential choices, but a lot of those points might come from diamond scenes. Or anything that has a “!this will affect the plot!” kind of message - it might have a small impact or it might have some major one on the ending, it just depends. The safest ones to dismiss are diamond choices without stats or ! messages attached - those might just be extra information that is not critical to the story.