I would put the OS on a SSHD and get the biggest conventional drive I could find for content. In fact, I would get a tower that had several drive slots and put in a couple. Games and video in UHD are fxcking huge files now, and you aren't going to find a SSHD at any kind of reasonable price that will hold all your shxt.
I have two 4 TB drives (full), two 2 TB drives (full), and three 1TB drives (again, full), and one more 4 TB drive I just started filling, and NONE of them even have UHD content, just regular HD content.
One game now is 60 GB before updates and saves, and one movie can be up to 30 GB. One puny SSHD isn't going to be enough if you're serious.
Even if you are only gaming, and not using the computer for media, you are still going to run out of space because some of the fxcking game updates are several GB at times. It really sucks to be in the middle of an update or online game when you are loading new maps and your system tells you it ran out of space and you have to stop playing.