If you have the port and money for it, I'd recommend a separate drive for the second OS. Windows is kinda notorious for stomping over GRUB if you rely on partitions for your dual boot.
If you're worried about installing to the wrong drive on accident, you can always physically disconnect the existing drive until install is complete, then plug it back in and set the boot order in the mobo config.
The PlayStation store is also a miserable shopping experience. If you don't know what game you want or just want to browse, good fucking luck finding it there. No screenshots, no gameplay, no user reviews, no related games to compare to, no info about if your friends are wishlisting or playing it. Just a choice of buying the expensive version or the more expensive version, and good luck figuring out which DLC is already included in the deluxe editions.