I will never again build without a ssd for windows.
It makes everything you do seem quicker.
Maintenance takes less time.
Apps open quicker, browsing is quicker thumbnails open instantly...
I rarely boot(I use sleep instead)
Today, 240gb is minimum.
You can get a fair number of games on a 500gb ssd which is now more reasonably priced.
A SATA based ssd is fine, either M.2 format or sata connected.
The pcie drives will have faster sequential rates, but that is really secondary to the much lower latency for random access.
Buy a ssd of some sort, and put all you can on it; you will not regret it.