Prerendering can only be used when your application only has static pages. When you want to render variable data (from the database) in your application, you're tied to server-side rendering, which requires NodeJS on the server (which seems to be provided through this GraalVM...).
So if you're in a position where you have NodeJS available on the server, I would surely setup server-side rendering. You will probably need to pass data from Spring Boot to React during SSR. I don't know how either Spring Boot nor React deal with this actually. I only have experience with ASP.NET Core + Angular.
I'm positive that something similar will be out there for Spring Boot and React, but I won't be able to help you with that.
You're (the web browser actually) using client-side rendering anyway, anyhow, anytime.
For SEO purposes, you enable either 1. server-side rendering OR 2. prerendering on top of this.
For prerendering, you need to run an