The Runtime filter allows you to view selected runtimes, or programming languages such as C++, Java and Python. With it, you can focus only on profiling specific languages, perhaps where an issue must be solved, without the distraction of languages irrelevant to the issue. An example is to remove the kernel frames, which will make it easy to investigate user-mode code alone.
The Mixed stacks option enables you to choose whether or not to show frames in different runtimes which are part of the same stack. Activating Mixed stacks by toggling the blue switch on will allow you to see syscalls that have been invoked in Java stacks, for example.