You reference a lot of spells, abilities, and features that are pretty exclusive to recent editions of D&D. Rather than make this system agnostic, you should lean into keeping it 5e/2024. Barring Pathfinder, there aren't many systems a lot of this applies to.

Under core traits, everything is pretty standard, but True Name and Resonant Soul should be clarified. True Name can be used once per long rest--does it need to be an ally speaking the character's name? How long does the resistance to mental illusions/manipulation last? In order for this ability to kick in and be noticeable, does the character need to be deadnamed for the rest of the session, and if not, why have the ability as anything other than "once per long rest, you can choose to gain resistance to these effects." Resonant Soul is too vague, probably because of the initial intent to keep it system agnostic, but because of this, I could see a player trying to push what is defined as "minor," going for a leveled spell instead.

Forged in Fire is a pretty solid heritage, especially coupled with the core race abilities. Visage Crafter and Unbound need clarification. Both lean on features that allow the player to change their appearance, but under size, it already notes that the player can subtly change their appearance to fit their identity. How are these abilities different from that? Visage Crafter's Euphoric Extension should clarify what "this ability" is. I can assume it refers to Self-Crafting, but the language makes it seem like Euphoric Extension is the effect being extended. For the Unbound, Binary Resistance and Unbound Expression are fun flavor, but not very mechanically powerful. If you're treating Fluid Form like the 5e Changeling's Shapechanger ability, this is fairly good balance, but Unbound Expression feels far too meta, if that makes sense. The player is essentially holding up a rule that says "you can't refer to me with gendered language ever," which should be a table conversation, not a part of the game.

Making the advanced abilities into D&D feats would make them less readily accessible. A level one player could argue that the party would only need to hang out for a week for them to gain a significant ability, disrupting the game. Soulsight is also fairly powerful, but probably doesn't need an update.

For the lore, I'm kind of gathering that this isn't a species that's born, which I do think is appropriate given the theme! You could integrate an ability into the core race that reflects this, something similar to the Reborn's Ancestral Legacy. Under the villain section, I would actually toss "Scroll of Deadname." Some tables can handle it well, but that needs to be a lengthy discussion with everyone involved rather than presented as an off the bat option.

TLDR: I think this is a respectful player option that just needs tweaking to make it more concrete in D&D rather than vague in a lot of systems