There was a thread about this not long ago and I was given a better description of the modes. Since then, I got to find out the exact changes each mode make and found out that there was a hidden mode as well. I'll explain the changes for each mode.
Classic Mode:
-- This mode makes no changes at all and is pretty much the same speed and damage as the Quake games. 100% Game Speed should be real-time-seconds.
Hardcore Mode:
-- It multiplies the TimeDilation by 10% which is then multiplied by the GameSpeed. It makes everything faster... TimeDilation=1.1*GameSpeed.
-- It adds 50% damage then what the weapons are set and any other damage inflicted. Damage gets multiplied by 1.5... Damage*1.5.
-- It only multiplies the player's JumpZ by 10%... JumpZ*=1.1.
Turbo Mode:
-- Everything that Hardcore Mode does.
-- It multiplies the player's movement variables by 20% instead. Here are the ones that change; AccelRate, AirSpeed, GroundSpeed, JumpZ, and WaterSpeed. Those variables are multiplied by 1.2.
Lightning Mode:
The hidden or unknown mode that was not added in the mode list for who knows what reason... maybe its too fast?
-- This mode only works with Hardcore mode from what it seems in the code and multiplies the TimeDilation by 25% and not 10%... TimeDilation=1.25*GameSpeed.
-- It also does everything that Hardcore does.
If you want to play Lightning Mode you will have to make a mutator that sets the bChallengeMode to true on the DeathmacthPlus gametype and its subclasses.
There's also a hidden/unknown gametype that wasn't finished or added to the gametype list. That gametype is called "Lightning Deathmatch" which is the same as DM except that it has Lightning Mode ON as default. I checked this gametype out and noticed that bots wouldn't spawn, meaning that it may not have bot support but it can be played on any DM maps in single player and maybe multiplayer.
In order to play Lightning Deatchmatch you will need to add the following lines at the bottom of your Botpack.int file when opened with Notepad...
Code:
// Lightning Mode //
Object=(Name=Botpack.ChallengeDMP,Class=Class,MetaClass=Botpack.TournamentGameInfo)
Preferences=(Caption="Lightning Deathmatch",Parent="Game Types",Class=Botpack.ChallengeDMP,Immediate=True)