I sideloaded the Amazon Kindle fonts (Bookerly and Ember) and a few others using the builder at https://crosspointreader.com/fonts obviously you need to be running CrossPoint to load the fonts so have that flashed on first.
You can download the Kindle fonts from https://developer.amazon.com/en-US/alexa/branding/echo-guide... if you don't already have them.
That said the Clara BW is still my preferred e-reader as I find the larger screen better for longer reading sessions however you really can't beat having a tiny 3.7" e-reader with you everywhere. All those "micro waits" at places and I can read a few pages or even a chapter of a book rather than using my phone for nonsense stuff.
Another tweak I do is use the ePub optimiser at https://inky.crossink.dev to give me more "friendly" ePub files for the X3. I didn't have any issue with my regular ePubs but this optimised ones open faster and do look a bit nicer overall so it is worth the few minutes it takes to optimise all your books IMHO.