that's a large Dutch Guyana
i'm curious about the Caribbean, with such a large and close Guyanan colony along with their existing north american colonies, i think it would be very possible for the dutch to get large parts of the south and eastern Caribbean. Maybe Jamaica, most of the Antilles and if they play their cards right Puerto Rico?
Cannot say really regarding the Caribbean.
An ATL Dutch Guyana would have either resembled the map below (including possibly the Brazilian and Colombian parts of the Guiana Shield) or the above, which include river borders on the Amazon, Rio Negro, Casiquiare and Orinoco though it is difficult establishing to what degree the rivers running parallel to or nearby the Guiana Shield.