Know that the two dimensions of a diagram are insufficient to express the confluence of logical data flow, physical data flow, dependencies, the infrastructure

Know that the two dimensions of a diagram are insufficient to express the confluence of logical data flow, physical data flow, dependencies, the infrastructure stack, the users and their use cases, commercial arrangements, legal entity boundaries, concurrent change initiatives, and boxes for the systems themselves and their fractal decomposition of modules and submodules. Basically, pick your battles and just draw what helps communicate something.