So I've pretty much planned most of my PC out.. thinking I'd finalize storage.

I use my setup for games, watching movies, and some video editing. I have a Samsung 990 2TB that i'm going to be partitioning and want another drive for long term storage, 4 TB size. SATA 2.5" seems like the best option for price but 7200 hdds are so much cheaper. Does it make sense to go spinning disc route or stick to SSD? I am pretty sure I don't need to go nvme for it since it's going to just be storing pictures, videos, files, etc. I am also a bit concerned there might be an annoying whirring noise. What is the best option for something like this? I just want to secure important and meaningful files.

By now you've probably already made a decision but I'll say SATA SSD. Speed won't be much of a concern if you already have an M2 for OS and gaming but I personally love that a sata can be shoved anywhere while an HDD should be properly mounted.

My use-case for HDDs is setting up a RAID array for higher certainty of preserving files into the future but single drive HDD or SSD can both fail so backing up important stuff to externals makes the most sense if your important files are small/few