No it's not safe. Even just turning on power at full-on stock settings is fraught with hazard... take a look at
in-rush current and share my terrors.
In the end everything in life is just a balancing of the risk-reward equation so if I want to play a game I have to turn it on. The same with if you want a tad more performance... you'll just have to take appropriate care and not go to far. But don't do it if you aren't getting any real improvement because, if there's no reward there's no balancing the equation. And nature hates
unbalanced things.