I haven’t been working in a company big enough so using process mining and simulation was economically valuable. My experience is in smaller companies, the largest one was with around 500 people on the business side. But it was still a startup, so processes were changing faster than we could possibly map them. So my advice on this topic is very limited, however, I have been researchinging this space for a while.
Celonis is one of the leaders in the process mining space.
As for the process simulation, once the process is mapped and converted to BPMN diagram - you can run it in Camunda workflow engine. Whatever tool for process mining you chose, you want ideally to be able to convert the output to BPMN format. It’s the standard for describing processes and you will be able to simulate it in most of the tools available.