You can have as many functions as you want in a flow. Although, be mindful of the functions operations and complexities. Some functions, such as Aggregation, OCR and AI can consume more resources than other functions.
When setting up Javascript and Containerized functions, you can set the maximum resources that they can use when being run. Be aware that if the resources are set too high, the flow may not have enough server resource to run. It is at this point that you either need to split your process in to multiple flows or add additional compute nodes to the environment.