I’m not sure how the Extendify plugin made it onto my WordPress build, but it did and it is offering Guttenberg patterns related to galleries. These patterns are preset for image arrangements. But they are not necessarily sliders nor do they offer any advanced functionality other than well laid-out placeholders.
Here, I’ll take a screenshot of some of the options (both free and Extendify Pro)
This is manageable from within Gutenberg
Custom Post Types
I’m not sure how these patterns are managed. There does not appear to be the need for a CPT.
Patterns sort of their own styles. WYSI kind of WYG
There is no native lightbox support.
Captions might not be supported here unless the Pattern accounts for it.