I want to digitize negatives with a Sony mirrorless camera. Do I need a copy stand?
No. There are other ways. You can use a tablet or phone, light table, lens adapter, etc. Google 'digitize negatives with digital camera` for options. Among top results you can see one that uses a tablet and another with a light table. Nikon makes a lens adapter for negatives too and it may fit some Sony lenses or you can use an adapter to fit a Nikon lens onto the Sony mirrorless.
Copy stands are for duplicating prints and documents, not film. While you can use a copy stand with macro lens and light box, using a slide copier is far easier and cheaper.
Except for the film carrier, capture with a slide copier is the same for slides and negatives. The images also need to be processed differently. For negatives, the orange mask needs to be neutralized and colors inverted.