I have partitioned every storage device (HDs, SSHDS)on every build we've done over the last 20+ years so I am a big fan of partitioning. I generally don't partition SSDs tho as most users aren't buyinmg them big enough to make worthwhile. However 50 Gb is way too small.
With modern games at 40 GB, two gaming partitions is a bad idea
50 GB is too small for backups recovery.
500 GB is too small for everything
Scenario 1 - A 120 GB SSD and 2 TB SSHD:
Remember 120 GB = 112 GB of actual space, 95 GB after leaving 15% free space. Here we put the OS and drivers / utilities on the SSD. In time your OS footprint will grow to 80GB if you are astute windows user. I am asked to clean the junk off 120 Gb OS Only SSD drives all the time.
The SSHD gets partitioned to user needs and usually the 1st will be a gaming partition as the outer edge of the drive is twice as fast as the inner. Sizes vary by user but the most common choices are:
Games
Programs
Data
Backups
On a 2 TB drive with equal partition sizes, each partition would hold 465.72 GB of files. This works extremely well as the games on the SSHD are on the fastest part of the drive but more importantly, the built in SSD on the drive will store your most frequently used files .... less benefit if you play 8 different games a day but if, like most, you will play say FC3 and then move on to FC4, your games will load at SSD like speeds and when you move onto a new game, the old files will automatically get moved off and the new game's loaded on.
You can repair a fudged OS by restoring it from a image file without having to worry about programs. You can even wipe the drive and install fresh. You will have to install programs over themselves to set up the registry entries for them but all custom toolbars and customizations for the programs, etc will remain intact.
Scenario 2 - A 240 GB SSD and 2 TB SSHD:
User specific and everything above applies, you could do one partition with OS and programs if it's a work and play box with everything else as above (minus programs partition of course) or if more gaming oriented, split it into 2 partitions of about 112 GB. Again, remember that since manufacturers redefined GB back in the mi 1990s, each GB of storage = 0.93 GB or actual file storage space.
So...
A. 112 GB for OS / Drivers / Utilities / Programs .... rest on SSHD
SSHD gets Games / Data / Backup partitions
B. 112 GB for OS / Drivers / Utilities + 112 GB for 2 -3 games on fav games partition .... rest on SSHD
SSHD gets Other Games / Programs / Data / Backup partitions
I'll note that on my test box, which several peeps use, I keep moving their game locations around w/o telling them. No one notices whether they on the SSD or SSHD.
Scenario 3 - A 500 GB SSD and 2 TB SSHD:
Here's I'd do the a 233 GB OS and Programs and a 233 GB "Fav Games" partition....
SSHD gets Other Games / Programs / Data / Backup partitions
If you are not going to get a SSHD or HD, then I'd make 1 partition for the OS and 1 partition for everything else.