What kind of changes can we do with programs when we scan in 3D

Hii everyone! I wanted to buy a 3d scanner for help me in my works. (Fashion design and accessories...) And I wanted to know before if it was easy to modify a file after scan. For example : I scan my cat head, I reduce the complexity of the mesh, okay... But Then I want to do it geometric and then change details, like ears etc.. For make an accessory or cool collar then. Or scan a human head for create on top of it some Masks or face accessories etc... Because on videos i just saw how to clean the model, or change a little bit of the mesh for simplify it. But i never saw a video with real changes, like actually work on the file. (I work with fusion 360, but thinking of buy Rhino, with I feel it's easier for free modification). Thank you! And have a nice day !

The term easy is relative. There is a learning curve with any complex modeling software. Once you get past the basics with any 3d CAD or modeling software it is relatively easy to change any aspect of a 3d model. You can change a human head to a cat head if you wanted to. Rhino is definitely easier than Fusion 360 for those types of changes though I have not used it. I have used Fusion360.

I would recommend trying out some free or low cost programs to get your feet wet and see what you like or don't like.

Blender 3d is a polygonal modeling software (free).
Moi3d or Plasticity are 3d CAD (relatively low cost).
Zbrush is industry standard for digital sculpting but on the same level of cost as Rhino.

Good luck. Modeling in 3d is a total blast and a ton of fun.