So this is a very abstract recap of what I did at work to achieve this:

let factor = 0.3; // whatever number
<ReactPlayer style="width: {factor*16}vw; height: {factor*9}vw" />

Provided there are no SyntaxErrors/Typos in there, this should work, but even if there are, you get the idea. You would then be able to control the size of the video via the factor variable (even change it programatically if you want to downsize it on scoll for example).

You can borrow from what Bootstrap 4 has done with their embed utility classes.

getbootstrap.com/docs/4.1/utilities/embed