i have lots of examples and tutorials about the modwave and wavestate on my youtube channel that answers your questions.
The main thing to remember is that the modwave can not only use samples (like the wavestate), but that it's also possible to convert samples to wavetables. And that is a huge difference when diving into sound design.
Here's a tutorial explaining how to create your own wavetables for the korg modwave
<iframe width="560" height="315" src="
https://www.youtube.com/embed/lVDW8WQfwpQ" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture"></iframe>
And here's a tutorial where i show how to create a wavetable from a picture.
<iframe width="560" height="315" src="
https://www.youtube.com/embed/0kbZF4gURU8" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture"></iframe>
Here is an example song i created with only the korg modwave and custom wavetables
<iframe width="560" height="315" src="
https://www.youtube.com/embed/Bbx5VxXGeT0" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture"></iframe>
based on your mangling question, here's an example of what the modwave makes it unique when working with wavetable positions. In this example i created a vocal sample with my own name and with the modwave you can select start/end points in that sample and the speed of the sample, all in realtime (and that's just the start of what you can do).
<iframe width="560" height="315" src="
https://www.youtube.com/embed/iHU3OFPcJZY" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture"></iframe>
When refering to samples, here is a tutorial how to create a sample library for the korg wavestate (but it works exactly the same for the korg modwave)
<iframe width="560" height="315" src="
https://www.youtube.com/embed/7jVJzx_CVmo" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture"></iframe>
There are a lot more examples and tutorials on my youtube channel, but i hope these couple of tutorials are answering your question.
if you got any further questions don't hesitate to ask.