the problem is that in theory these are all safe, but in practice there is buggy hardware and so they are not safe.
So you need to take a risk at some point, and if the system crashes, don't use that option any longer.
These are the sorts of possible problems (along with the performance issues) that make it so that Fedora doesn't default all these things to the most power saving mode.
Some people seem to forget that the best way to have a computer save power is to never buy it in the first place. Computers are purchased to get things done, and that requires using power. How much power should be used depends on how valuable the result is to the person paying for it.