1) MOST GAMES do not benefit from an SSD aside from loading times
2) A few games like PREY can STUTTER without an SSD due to texture loading (no idea if they fixed that or not in Prey). That's pretty rare.
3) Stick with an HDD that fits your capacity requirements.
4) Tradeoff in HDD RPM is performance vs noise (7200RPM of similar drive architecture is faster than 5400RPM but noisier). I'd probably go 7200RPM for games though and just set Power Options in Windows to shut down after 20 minutes of inactivity.
5) *just see PCPARTPICKER storage section. filter down as needed.
DESPITE what I just said for some reason the WD BLUE 5400RPM drive is pretty good value (price per GB):
https://uk.pcpartpicker.com/product/2Qqbt6/western-digital-internal-hard-drive-wd30ezrz
And here's a 2TB Seagate 7200RPM:
https://uk.pcpartpicker.com/product/CbL7YJ/seagate-barracuda-2tb-35-7200rpm-internal-hard-drive-st2000dm006
A higher CAPACITY drive performs better on average than a lower capacity of the same RPM... for example if you filled up a 2TB HDD but compared to a 3TB HDD with the same data (so 1GB well actually 930GB or so free) then you get slightly more performance because the same data is on average spinning faster as its closer to the edges of the platter.
Can't give you exact numbers but the inner platter is often about 50% the performance of the outer platter on the same HDD.
I also recommend making backup IMAGES of your Windows (c-drive) so that may take up roughly the same amount of space as what you use of c-drive depending on your backup settings (I use Incremental, auto-delete, 2nd highest compression).