I have the games installed on my SSD drive C. I moved my documents folder to D as it has so much space there. Naturally, the EA documents folder with all my CC/store stuff went into D.
The game runs fine so far. I haven't actually played yet as I'm still carefully setting it up with mods and CC and have yet to actually save a single session.
I still have ample space on my SSD to fit the EA folder and it's 10GB of CC/stuff.

My thoughts are that the game will run even better if it's all on a single drive. Is this the case?

If so, is it as simple as creating a Documents folder on C and moving my EA folder over to it?

I have Windows 10, NVidia GTX980, 16gb Ram. 130GB free on my SSD:C drive and 2 TB on my D Drive.

Thank you for any information. I'm hesitant to just try it if this is a pointless endeavor. Makes sense though, that it would be even quicker if it was all on the SSD.

I've actually read that some and am definitely intrigued about it and may implement if the game has problems down the road. As it is, it's running quite well in my tests, but it's still early in my installation of everything and I haven't actually played and saved.

I did have one issue upon installing my Story Progression mod (AM), but I believe it happened from me either changing households in edit world/town mode and slowing it down there or that I hadn't deleted my caches after installation of the mods.
Either way, I have had no further slowdown issue since.

I really want to know from someone who might have both the game and documents folders on their SSD if performance is notably improved over having them on separate drives?

I am familiar with the symbolic mklink I may have to do if I move the folder to my SSD, but not positive that's necessary. And btw, learning about that symbolic link made me a little concerned when I originally just moved my documents folder over to my D drive to start with. This was when I was setting up my system, not the game, but hopefully that didn't mess anything up.

The only thing I could suggest is keeping your operating system on it's own dedicated drive.

After putting games on their own drive they do load faster, though I didn't notice any decrease in time for loading up TS3.
Tested that with an SSD an HDD and even had the documents folder on the same SSD and even on a different one.

Seems more like a limitation of the game itself rather than a hard drive or CPU problem.

Thanks for that answer, Nitromon. That makes more sense to me now as I was concerned about the amount of writing and increasing data for the SSD. Especially with extra saves, CC added later(which I'm hoping to not do, buuut) and the many error codes that will undoubtedly be created if only from Overwatch. ( Some pop up almost immediately upon starting a world, such as a stuck sim/etc.)

I will consider the RAMdisk for the user folder as that solution prevents the moving/linking of the document folder, doesn't add a bunch to my SSD and adds the speed. However, I've noticed that the SoftPerfect RAM Disk available says it's good through Win8 and I'm seeing some incompatibility issues with Windows 10 so far. Might have to wait a bit.