All data should be sent to Eloqua. The operation to do this is simplified compared to the xforms. You don't need to use invisibe fields to add information about the lisence in invisible fields or the Submit button.
Add the form element Eloqua Mapper to the form. The other information you need to add is Eloqua Form HTML Name to make sure that the information is sent to the correct place in Eloqua.
It should not be necessary to add information about business unit to the form. If you would like to add this or other information invisible to the user, you could use the form element 'Hidden predefined value'.
In addition you will have to have filled out Eloqua HTML Field Name on each form element.
Sending mail with form data or as a receipt should not be done through Episerver, but from Eloqua. If there are any business units that don't use Eloqua yet, you could set-up a mail from Setting in the form-block.
You should avoid storing data from forms in Episerver. It should always be sent to Eloqua, even if the information doesn't have immediate value for the sales process.
From May 1st 2017 no more data should be stored in Episerver. You should make sure that this is turned off in Settings for the Form-block.
Storing data in Episerver is not according to best practice outlined in Visma's Privacy statement. Even if it is possible today, there will be a cut-off data when this is not allowed. The reason for this is new data regulations in EU. Not upholding them could lead to bad PR and a fine from the authorities.
If you end up having data from a form in Episerver, it is found on the 'Select View'-dropdown.