Here in the states at local events we direct, we tend to just keep the music at a moderate level and jam it the whole time.
Don’t know about the CPU, but to me, turning it up and down, etc. is unneeded at the local level. Kind of like the ER Rack requirement.
As long as you can hear the announcer, and the lifter and other judges can hear the head ref you are good.
I think it adds tons to the environment. It’s just like a good announcer and we get lifters coming back every year specifically to meets we direct because the atmosphere is cool.
As far as tunes, I play all kinds of shit.
When people are arriving and in between sessions, etc. I usually play a little more mellow stuff. Buddy Guy, Stevie Ray, Zeppelin, Pink Floyd, Hendrix, etc.
During the meet I run mixes of standard stuff. Metallica with a bias towards Garage Inc. (really dig somoe of the merciful fate and motorhead covers) and Ride the Lightning, Priest, Megadeth, Maiden, System, Audioslave, Foo, Nirvana etc.
I don’t really play any rap or death metal because like you said you need to keep it clean and IMO you are better off staying relatively mainstream, especially if you are anticipating a big spectator turnout with families of lifters, etc.
Just some thoughts off the top of my head.
Good luck with the contest. When is it?