There was an interval where there was no overlap, but, after a certain point the story went through both comics.
Fantastic Four 600-604 happen at the same time as FF 12-16 and overlap heavily. I dunno how they;re collected, but they should really be read alternating between titles after each issue, I dunno what you'd get revealed out of sequence otherwise. Might work perfectly well.
Fantastic Four 607 and 608 happen at the same time as FF 20 but aren't really needed to be read together.
Fantastic Four 610 and FF 22 are the same story from different perspectives, and FF 22 contains the conclusion.
Fantastic Four 611 and FF 23 are the final issues of Hickman's run, and while they're totally separate stories neither one is skippable in the grand scheme of things.
Fantastic Four was basically shipping twice montly from 600 onwards, with the FF issues typically (but not always) focussing more on the kids. FF has an awesome Johnny Storm\Peter Parker issue and the conclusions to all the Inhumans\Negative Zone stories. F4 has a great Thing story, the set-up for Black Panther in New Avengers, and introduces AIM island as seen in Avengers.