The performance and overall behaviour will still depend on your own code, outside of the framework you are using. In other words, you have correctly listed the major factors which will influence performance, but your own code will have such a significant impact on it that it's almost impossible to tell in advance.
Offhand, I'd say that you need to characterize some things about your application in more detail:
- You say that each request will be CPU intensive, but what do you mean by it? Will each request take 1 ms? 10 ms? 100 ms?
- Do you access a database? What are the characteristics of your database?
- Either with the database or without it, do you have any disk IO? How significant is it?
... but if your application is really simple, does not hit the disk much (or at all.. your request may be read-only and everything gets cached), and you are CPU-bound, simply sticking enough CPU cores in your server will be the most significant thing you can do.