In most cases, whether LoadRunner is simulating 1 user and having them do 1k actions at the same time or 1k users and having them do just 1 thing, won’t make a difference. Because generally the question of scale is really about number of simultaneous connections. But it can make a difference due to caching and state changes.
Simple example, suppose you want to tell the user something the first time they take an action on a per day basis, suppose that determining what to say takes a long time. If you have 1k different users being used, then the message is definitely going to be composed 1k times. If on the other hand, you have 1 user repeating the same action 1k times, then at least some of them can be expected to skip composing the message, with the corresponding reduction in effort.