The shortest one is for a single communication. Think "created in a meeting, used in a meeting". These need to have zero friction to make, their maintenance life is measured in hours, and quality doesn't really matter. You'll do best to use a whiteboard or paper. Take a photo with a camera if you regret thinking it's of no use in 24 hours, and convert to one of the other formats.
The second one is for a planning stage. You might argue different design decisions and their merits. You need to be able to point to a few different solutions to keep the dialog going. These likely need to be pre-made (can't make them IN the meeting as that's too time consuming) but they should be easy to adjust during a series of meetings. Here is where you may want to use some simple drafting tool or Visio or similar. This type of diagram also works well for a presentation where you want to show a group of people a design/architecture - but you can then throw away or archive the presentation. The key is that these diagrams aren't live documents. They have a lifespan limited by some specific event such as a meeting, a presentation. You may be tempted to keep them, but it will be a historic artifact. A recording of the presentation is more useful than the diagram itself. The key thing to remember is that they are useless for describing an evolving system as no one has ever successfully maintained/updated a set of Visio drawings over time to accurately reflect the system they described.
The third one is when you want to achieve that impossible goal of having a living document. The only way to have a living document for software is as code/text, since the only source of truth is version control. Either it needs to be constantly modified, or (ideally) it has to be constantly auto generated. The quality of a generated document is going to be nowhere near a hand-drawn visio thing, but on the other hand it will describe the system, unlike the visio document which was last updated six years ago.