Generally speaking, practicing the piano is done by machine, and playing is done by hand.
I think you'd better not choose the old piano as soon as you start, because the old piano may have some minor defects. The violin is strictly a worn product, although some parts will be better than the new one, especially the position of the tuning shaft. But you can't see more problems, such as the wear and tear of the bridge. If there are any cracks in the fuselage, it will definitely affect the sound quality. It's best to start with a new piano.
My teacher says playing the piano is easy to wear out, but I really don't know if this statement makes sense. So use the ordinary piano as soon as you come up, and don't pursue sound quality or anything.
The piano box is not a big problem, it is nothing more than a portable one with one shoulder and two shoulders. Choose any style you like. One thing to note is that there is a bow in the violin box. Put a bow in it when you buy it to see if it fits. Don't buy it if the bow will rub against the box. I always feel that it will affect the life and sound quality of the bow. I can't say whether there is any scientific basis for me to say this, just from my own experience.
Another problem is the lattice where small things are placed at the head of the piano box. Personally, I suggest choosing a square one, because you need to put spare strings, rosin and tuners. If the fit with the lattice is not enough, the rosin will move or even crush. Also, be sure to cover the lattice, and then close the piano box to see if the contents will fall out. It is not good to break or scratch the piano.