From a lookup field settings, it's possible to add additional columns to show each of these according to the selected item.On SharePoint Online these additional columns are available and can be displayed for instance in a list view.
At the moment, these additional columns are not available from Nintex forms (For O365 new responsive forms)
It would be very useful if these additional fields could be available in Nintex Forms to show them in a form.
Thank you very much for posting your feedback for our review. At this time, we will not be adding this request to the near-term backlog, as we are focused on other highly requested features. However, we reevaluate requests every quarter and will reach out if priorities change. Please keep the feedback coming as it is critical for our longer-term planning.