Hi Sebastián Ardila,
Thanks for reaching out, these are great questions!
The Online version of Insights includes all of the functionality of the ArcGIS Enterprise version, with the exception of features that are specific to ArcGIS Enterprise, such as ArcGIS GeoAnalytics Server and direct database connections. Here is an overview of what’s new in the online release.
As for the Enterprise version of Insights... At a minimum, to run the installation you must have installed Portal for ArcGIS and ArcGIS Server, either on the same machine or separately in a distributed environment. Insights also requires ArcGIS Data Store and ArcGIS Web Adaptor to run. These ArcGIS Enterprise components must be installed before Insights can be used.
Hope that helps!
Nathan