As of now, BoldGrid Post & Page Builder doesn’t work well alongside Glutenburg. We’re currently working to ensure BoldGrid is compatible with Gutenburg before its full integration into WordPress installation. Sorry for any inconvenience.
Quick update to this answer: Gutenberg is now fully integrated as the default editor in WordPress version 5.0. BoldGrid allows you to use the default editor (Gutenberg) or use the BoldGrid Post and Page builder for content creation or modification.