What are the tournament/pro level graphics settings for Unreal Tournament 2004?
There are a number of visual and audio settings that are commonly tweaked by competitive players.
Visuals
Many players in UT2004's old competitive community used the mutator UTComp to force a default player model + a brightskin. This is of course only available on servers using the mutator.
On servers not running the mutator, users can force a default model for all opponents via the User.ini file :
[XGame.xPawn]
PlacedCharacterName=Gorge
PlacedFemaleCharacterName=Rylisa
Only certain models can be forced, and you must play as one of models you force. I believe these are some of the available options:
Males: Gorge, Xan, Malcolm, Brock
Females: Rylisa, Tamika, Sapphire, Enigma, Ophelia
I know many competitive players who would set lower their texture quality to the very lowest, to reduce clutter. I don't believe this was allowed in tournament play, but that would vary by tourny rules.
Audio
On servers with UTComp, many players use CPMA style (damage dependent pitch) hitsounds.
Almost all players turn off their music, and some adjust their ambient volume and roll-off settings in UT2004.ini :
[ALAudio.ALAudioSubsystem]
AmbientVolume=0.125000
RollOff=0.400000
As you increase ambient volume, you can hear locational sounds such lifts and creaky boards more clearly, but there is also more environmental noise such as thunder, water, etc. So, it's a trade-off.
Reducing roll-off is likened to cheating, because decreasing the value decreases the dissipation of sound over distance; sounds travel farther. Competitive servers often use a 'lock roll-off' mutator that limits the value to 0.4 (default is 0.5.)
Other
Check out TweakGuides' UT2004 guide for additional information on configuring your .ini files.
There are none. You can tone your graphics settings as you like and maybe set a custom crosshair and change the HUD size, but tournament holders sometimes have a strict policy of what the HUD has to look like.
And, you can't redefine or modify hitboxes in UT 2004, if that is what you mean. Playing with such values can get you kicked by the server security (Safegame, AntiTCC etc.) real fast.