If your textures are smaller than 4096 (both actual texture size or forced texture import settings), you shold see the same result with and without Amplify Texture. Of course, this plugin will still allow you to use unlimited number of textures and will stream them automatically.
However, if you have source textures with sizes larger than 4096 (even though Unity only imports up to 4096), you should get more detail when zooming in when using Amplify Texture, because we add the full resolution source image (even if 8192x8192, 16384x16384, etc..) to the virtual texture, instead of the one limited by texture import settings. We read directly from the image file, not from Unity assets.
In conclusion, using Amplify Texture you still have full control over texture density, like you do when using Unity's regular texturing system. If you use the same texture density as before using virtual texturing, you still get the unlimited number of textures and streaming for free.
I'm creating an interface to visit a house from outside, inside and more options... For the outside, it must be the more realistic as possible, so I used HDRIs for the lighting, and now I want to see if it's possible to have better textures. But I think I don't have textures bigger than 4096 so I will see whath I'm going to do. Thank you for you help and your explanations !