part of why I've been procrastinating. telling myself I want to read Shadow and Bone first and then. NotI read Six of Crows without having read the Grisha trilogy, and I understood the world pretty easily. I would recommend reading Shadow and Bone before Crooked Kingdom though, since some of the characters from it appear in CK.
Honestly, I read the Six of Crows duology before the Grisha trilogy and I'm glad I did because I don't think would have read SoC had it been the other way around. You get kind of more of an in-depth explanation about the magic system in the Grisha Trilogy but it's not super complicated so you'll be fine if you don't read it.
Kind of recommend just going straight for SoC because the Grisha trilogy is kind of terrible.
but that's just my opinion