You should be able to use the Cwicly blocks in the Gutenberg content editor when creating posts and pages. You should also have access to ACF Pro from the Cwicly plugin.
A big feature of Cwicly is the ability to create theme templates using the Full Site Editor. Since GeneratePress is not a block-based theme, that option won’t show. Also, there may not be coordination between your GeneratePress Customizer settings and Cwicly styles (I’m not sure how that will work). Note, there is a setting in the Cwicly advanced settings area to disable some Cwicly style related to Flex should there be a conflict.