The generated react living alongside custom react sounds similar to MUI's low-code drag-n-drop editor that they're working on (https://mui.com/toolpad/).

Looking at the demo, does Plasmic have any killer features that MUI's offering doesn't? At the moment, MUI's main limitation is that it can't connect directly to a database: you have to go through an API, or write an API route for each app that proxies the SQL queries.