CS:GO specifically is a CPU driven game, higher clock rate = higher FPS. For gaming, you will definitely want boost activated.

For normal daily use, it depends on what you're doing with it and your tolerance for slower performance. Normal net browsing and some light streaming will be fine but if you're using CPU heavy programs like photoshop or compiling large amounts of code, performance will suffer or it may not run at all. Using photoshop as an example requires a 2ghz chip minimum so I can't say for sure it'll even run well enough to be usable without boost.

The only drawbacks of using the boost feature is a higher operating temperature and a faster battery drain if you choose to use boost while on battery. The operating temperature is regulated to safe levels automatically and that's not a very powerful chip but it will be a bit warmer than without boost. The boost feature is also disabled while on battery as a default. You'd have to change that manually if you wanted to use it.

There's really no practical downside to running with boost enabled all the time. It'll only activate when needed.