According suggested structures “targets” are the right way for campaigns.
So you will get a list of “targets” which views or answers the campaign.
As soon as they answer, you should convert it to leads or contacts according CRM docs.
What is the suggested way to convert it to “leads” or “contacts”?
Technically there is no problem in sending out Campaigns to any of the record types: Contacts, Leads, Targets, Users, Accounts - that is a matter of your own process design in your company.
Part of that design involves getting just the right level of conversion steps - keep them to a minimum if you can. For example, few companies will need all 3 levels (Target > Lead > Contact) and it’s ok to leave out one, to save effort on the conversion processes.
And in the Campaign Status subpanels you have a “Add to Target List” button that let’s you retrieve that group of people (for example, the ones who “viewed”) to store it and process later.