Could you define "best"? I think it depends on your requirements. There are many tools available. Here are some I suggest. * Excalidraw https://excalidraw.com

Could you define "best"? I think it depends on your requirements. There are many tools available. Here are some I suggest. * Excalidraw https://excalidraw.com/ https://excalidraw.com/ + additional libraries for cloud entities * Diagrams.net, formerly draw.io * Lucidchart