Using section access would probably help you in this case; because all 50 users don't work with the entire dataset to start with. I expect Qlik's internal memory management to efficiently cope with these smaller portions.
Really splitting up the dataset into multiple smaller applications is not available (yet) in Qlik Sense. The functionality you describe is available in QlikView, and is called "Loop and Reduce" that generated similar dashboards with only a part of the dataset, based on the values in a specific field.
I want support for this feature in Qlik myself. See the following thread:
Found a (good) solution yet?
I have asked some people today during the "Visualize Your World" Virtual Forum event; didn't result in a satisfying solution just yet. But I did get some additional input, see this thread: https://community.qlik.com/thread/165488