Unlike the dracthyr visage, dragons choose their visage when they mature and in the “Visage Day” story, Chronormu spent many days consulting other dragons in order to pick her one visage which she will keep for the rest of her life. As for other creatures, I believe it is only 1 humanoid visage.
All dragons are intelligent enough for speech though, if a parent never spoke when the dragon was an egg or when it was born, I suppose it could avoid learning speech but generally, most dragons speak both the common languages and draconic.
Dragons can be really old. Someone like Kalecgos is a bit younger and is not nearly as large as someone like Nozdormu. If a dragon like Wrathion for instance, who has only been alive for a few decades, he will still be the age of a “drake” and dragons grow a lot throughout their life and he will be smaller than a full grown wyrm. This is why dragons come in many sizes, it’s because they age and grow in size continually.
Most dragon mounts are drakes and are very young and haven’t matured to the age of picking their visage and may not’ve learned to speak. Wrathion is the only exception having a visage and speaking very early in his life.
oh man, wouldn’t it be cool if our dragon friends who’ve been hauling our butts around all this time could actually fight alongside us as well? (visage shape ofc otherwise they’d be too big)
Let’s take the shape thing first. It’s not that they can’t, they don’t, at least not when on the job. And good thing, too, because turning into something wingless at a thousand feet above ground level is going to ruin everyone’s day.
Similarly, it’s not that they can’t talk, they don’t, at least while on the job. They were trained in the “reserved butler” style, not the “chatty cabbie” style.