For starters, even if it wasn’t a resource hog, a lot of people don’t even like the way motion blue looks, so it’s an easy one to cut from your PC graphics settings. It can be cool for certain genres, but downright annoying for others, so it’ll depend on your personal taste, but if you want to save resources and make your game run smoother – you know the drill.
Different games will have various settings for shadows. Do you really care how crist the outline of a shadow looks in a game? Are you even really looking at it? It’s the type of thing you’ll notice out of the corner of your vision, and you’ll notice if they were gone completely, but having “lower-quality” shadows isn’t really something to write home about in tears.
Now, as with most of the settings on this list, it’ll depend on the game itself, so your mileage may vary, but these are some of the first settings you should start playing around with.