#mermaid is the winner for most diagraming, especially inbuilt support in tools like Azure DevOps -- except for C4 diagrams where I still use #PlantUML.
From DanDoesCode: "Mermaid will be fine for most of your needs, but for anything more complex or for doing C4 models, I would fall back to PlantUML. Overall Winner: Mermaid" https://www.dandoescode.com/blog/plantuml-vs-mermaid