The person who got inspired by prosemirror and built lexical is no more at meta. Go to the repository and you'll find it's already in maintenance mode. Its promise of cross platform extensible editor is unrealised yet.
We used Lexical intensively in my company (Crisp), and I can confirm it's definitely not in maintenance mode. What's super cool with Lexical is the package/extension system. For instance, we use the Lexical markdown package a lot; it's not the gold standard yet, but since we have a large user base, over the years we've made a few PRs to the Lexical team, and they approved/reviewed the PRs in 24 hours.
About WordGuard:
There is no community behind it; the guy building it clearly wants no AI involved and even has his own internal Git hosting system.
Finally, there is no single user on WordGuard.
I see virtually no reason to use Wordgard over lexical.
I've personally been hoping for something like this for a while now. Especially a toolset that is not just targeting yet another SaaS or LLM or social media clone interface.
I don't know if you ever used Draft.js that FB put out some time ago, but it was a horribly buggy monstrosity that was a heavy lift to move away from. One could not write several paragraphs and edit them without losing a lot of work. I wouldn't touch "Lexical" no matter the marketing they put on top. I wouldn't be half as critical if it wasn't one of the wealthiest companies on the planet known for injecting billions into black holes while they raid every area of your life they possibly can for data to be used to manipulate socio-political matters everywhere. If they're going to do that, and release open source libraries, then at least make them good enough to be seductive. They aren't.
ProseMirror and seemingly WordGard have real thought and care put into them by people who have long made the DOM/developer experience and the writing experience priorities– not just their "mind share" for whatever dark purposes drive companies like Meta.
It's something to avoid for everything. They've gone further with nastiness than the other FAANGs IMO. Though alternatives may be hard to see, they exist, including for PyTorch. In many places it's zero sacrifice like with React.
I'd pick prosemirror any day over Lexical.