I don't know if you still need the info but I actually successfully downloaded the sims 4 onto my flashdrive while having origin installed onto my computer, I didn't have any problems not even lag it worked really well for me. I did this by installing origin onto my computer and then going to preferences in the application, then going to the 'installs and saves' tab and changing the location to an applications file on my drive, I started getting alerts saying that "games cannot be downloaded into this location" after a few weeks but it didn't make sense because I had played the game successfully. It ended up not affecting the gameplay at all. But one of the downsides to a flash drive is that because it is a detachable component it's easy to break or lose and my sister dropped my computer, breaking my flash drive. Now I am trying to figure out how to put the game onto an external harddrive but I am struggling a bit with the "verifying game files" load being stuck and I have reset origin twice now. If you are going to try it, I suggest doing what I did, having origin installed onto your computer and your games on your flashdrive.
