Final Cut Express 4

I understand that $300 is quite a bit of money, but probably you will be well served with iMovie, which is free. Give it a try.

As a personal note, I did buy FCE, and at the time it cost $200; I only did get on a promotion (or perhaps the physical store had marked it wrongly at $100, as that used to be the cost of the upgrade).

On the other hand, although FCP "X" cost $300, I paid for it in 2011 and have used it for the last ten years, and all updates have been free. (Of course, we don't know for how long this will continue).

No. Final Cut Express was a 32-bit application.

I believe the last version of OS where this worked was probably macOS Sierra (10.12).