How To Play Games at a Lower Resolution?

So I've started up a YouTube channel. I can record everything fine (although I have to lower my graphics a little bit), but my monitor's native res is 16:10, 1440x900, and YouTube's and Twitch's players are both 16:9, so I get the black bars in the sides of my videos. Obviously I can solve the problem by just setting the games to run at 1280x720, but I hate how the game stretches itself to fully fit my monitor. I've tried changing the res in the nvidia control panel, and it works for WIndows, giving me the black bars at the top and bottom (which I can live with), but my games still stretch themselves to fit the monitor. Is there a way around this? I think playing in windowed mode will stop it, but doesn't that decrease performance?

On your monitors settings menu search to see if you have the option set the aspect ratio to "Auto Resize".

Its what I do with my dell... Some games don't support my ultra wide monitor and the settings at default are 21:9, meaning that if the game doesn't support 21:9 it will stretch the 16:9 image to a 21:9 ratio. Setting it to Auto Resize fixes this so no matter what aspect ration you are playing it will display it with the appropriate black bars. and when you record games it will just record the image no the bars.

Hope that helps.

If that doesn't work play it in windowed mode.

@Grey_Eyed_Elf: My monitor doesn't have that option, but I tested some more games, and most of them appear to fit the monitor res when I set it to 1280x720, with the black bars on the top. Guess I'll just have to live with it for the games that don't. Thanks anyway!

Edit: Found an option to override the application settings in the nvidia control panel