Tutorials for those probably don’t exist because those are not common use cases for Juce. (Especially the dll one would be tricky because then a tutorial would likely need to get into nasty details like C++ ABI compatibility and how to create a plain C interface for the dll…)
Basically the Juce classes you need to use your audio hardware are AudioDeviceManager and AudioIODeviceCallback.
I wrote a simple command line program that outputs a sine wave and lets you type on the console to change the frequency :
There are helper classes like AudioSourcePlayer that inherit AudioIODeviceCallback and the Juce tutorials use those. However, since you wanted the lowest level example, I inherited AudioIODeviceCallback directly instead in my example.
Here’s another example that uses the Juce provided classes so you don’t need to inherit AudioIODeviceCallback and implement the sine generation :
