Depends on what effect you want to use. Generally, your own small membrane, 15 inch 2.53 is enough. If there is a commercial component, you'd better buy a better one. Except the wedding.
"Will Final Cut gradually replace Premiere or become the mainstream in the future?"
No, one is used on a pc and the other is used on a Mac. Users are different, and there is no meaning of who replaces who. If so, it is also Apple that has replaced Microsoft as the main computer system.
"Now I buy a Macbook pro, and some stores told me that I can help install some commonly used software, PS or something. Can I install Final Cut pro? "
It is safe to say that there is generally no, unless it is a private computer shop, they will install it for you. But be prepared. Definitely not genuine.
But don't worry, it won't affect the use. Of course, you can also go to a regular store to buy it, and then go to Taobao to have a look, and you will find something unexpected (I don't recommend piracy, the genuine version is too expensive. You know)
It doesn't matter if you don't buy it Apple's own editing software is imovie. Of course, professionals can't do it, but you can have fun.