Both files live in ShooterGame/Saved/Config/LinuxServer/. Stop the server before editing; ARK rewrites them on shutdown. Restart afterwards.
GameUserSettings.ini
The everyday settings under [ServerSettings]:
[ServerSettings]
ServerPassword=
ServerAdminPassword=changeme
DifficultyOffset=1.0
OverrideOfficialDifficulty=5.0
XPMultiplier=2.0
TamingSpeedMultiplier=3.0
HarvestAmountMultiplier=2.0
DayCycleSpeedScale=1.0
NightTimeSpeedScale=1.0
AllowFlyerCarryPvE=True
ServerPVE=True
MaxTamedDinos=5000
DisableStructureDecayPvE=True[SessionSettings] holds SessionName (the name in the list). On PenguHost this is set through the Startup variable SESSION_NAME instead, which overrides the file.
Game.ini
Long-form multipliers under [/script/shootergame.shootergamemode]: per-level engram points, per-dino damage, breeding intervals, custom harvest amounts. Example:
[/script/shootergame.shootergamemode]
MatingIntervalMultiplier=0.5
EggHatchSpeedMultiplier=10.0
BabyMatureSpeedMultiplier=20.0
BabyCuddleIntervalMultiplier=0.2
LayEggIntervalMultiplier=0.5
OverridePlayerLevelEngramPoints=...A Game.ini that only contains the section header is normal, because ARK creates it empty.
Which file?
If the setting is in the in-game host menu, it is GameUserSettings.ini. Anything with "Multiplier" that is per-item, per-dino or per-level goes into Game.ini.
Kowalski knows both files: "set taming to 5x and mature speed to 30x" edits the right one.