An answer with several parts:
The truth is that if you want real flexibility in making mockups you need to learn a 3D program.
Use Blender https://www.blender.org/ that is free, very powerful.
If your computer is slow, and I mean, really slow, (Pentium) you can download a legacy version. https://download.blender.org/release/ compare the date of release to the year you bought your computer. Do not go below version 2.5. That is ancient.
Look for tutorials on youtube on:
- Cloth simulation
- Cloth texture
- Importing shapes
- Light and Render
It is not very hard, but it takes some time. The advantage, besides having total control on your mockup is that the next design will take you just a couple of minutes to do, because you just need to replace the textures.
But if you are still intimidated, just make a simpler mockup that you can control.
Here are the source images:
But with a simpler setup you can, not only change the shape of the tag, but the texture and the cloth below. You can add perspective if you want.
I also agree with @Scott, the art of making real-life dummies is forgotten. It would be interesting to print a test in real life. This is especially true to things that will be, not only printed, but also cut. It will give you a real idea of the structure, and how sturdy the label will be. I suppose the star is only an example. But it is not a good structure to be used as a label.