My opinion: if the modes can be use interchangeably then MODE as OptEnum is right. If every MODE has a specific purpose, then Actions should be used. 

@morisson I think the easier way to get introduced into Actions is to check other auxiliary modules using them. For example: modules/auxiliary/scanner/http/mutiny_frontend_read_delete.rb Also you can just search for the string 'Actions' into the auxiliary modules tree to get  lot of examples : grep -r \'Actions\' *

Don't hesitate to ask if you have further questions about the Actions topic.