24Bit depth is also known as 8Bit color space which is the standard sRGB (16.7 Million Colors) depending on what reference and software you are using.
So 24Bit depth / 8Bit color space is the standard. The amount of colors will not cause any more load on the GPU but most likely you monitor cannot display 10Bit color space (aka 1 Billion colors /32Bit Depth.) unless you have a very nice monitor that starts at $500
For multi sampling that refers to something completely different. Much easier to google it than explain super sampling. But that will use more GPU power and create more heat. but the image will be crisper.