Question

Does building stuff from source on my computer really make them run faster or more efficiently than if I directly downloaded the binary instead?

Answer 1

In most cases, you'll see very little tangible performance benefit. There are highly computationally intensive applications (say, ray tracers or video encoding) where it can make a big difference, especially if the program's code is prepared to take advantage of different processor's features (such as different versions of SSE or other vectorization features), but for most general purpose software, the benefits range anywhere from negligible to minor.