Regarding dragons of any age, the fact that dragons are metaphysically evil does shift things in my opinion. Chromatic dragons are magical beings that are evil at their very core, and for them to be good would require, in my very limited understanding, some degree of magical intervention. And as for a wyrmling, I've never had to fight one in a campaign, but while I'd feel kinda weird about it, I don't think I'd mind that much unless the GM really leaned into it acting like a child. And even then, a chromatic dragon would probably act like a child the same way a serial killer is a child. Naive, maybe not fully understanding what they're doing, but still eager to hurt things, enjoying hurting things, and with no regard for the pain they're causing.
Regarding tieflings, I personally think alignment locking player races is the less interesting way of doing things. It takes away options rather than adding them. If you want to have it be that tieflings still feel an internal urge to do bad things because of their fiendish heritage, sure. That makes for interesting story. And to flip the script, aasimar feeling the internal urge to good automatically is an interesting direction. You can play an aasimar that wants to be evil, who does selfish, cruel acts, but is always dogged by an inherent, unwavering sense of conscience. The potential of that for a player is incredibly interesting, a villain who can never FULLY justify what they're doing to themselves, who no matter what will always know the difference between right and wrong, and be pulled towards right just like a tiefling will be pulled towards wrong. Both can ignore those urges, but they're still there and they still have to deal with them somehow. But those stories are cut out if you lock alignment.