polarbear's advice is very thorough and human, as always!
I have very little to add.
My dysgraphic-y kid also has beautiful handwriting--but it's super-slow, and clearly not automatic. Scribing, keyboarding, and speech-to-text are the way to go.
I second the SLP eval. LMB does work, and it's an excellent product--but don't forget, they're still selling a product. As they say, if all you have is a hammer, everything looks like a nail. A language eval will get you a broader picture.
For inexpensive alternatives to LMB, we've had good experiences with the OG-based home program All About Spelling/All About Reading.
