Please post the output of `qdbus org.kde.KWin /KWin supportInformation`. Also did you enable HDR or change color accuracy settings?

Setting status, since we're waiting for a response.

(In reply to Vlad Zahorodnii from comment #1)
> Please post the output of `qdbus org.kde.KWin /KWin supportInformation`.
> Also did you enable HDR or change color accuracy settings?

My monitor isn't HDR-enabled to begin with, color accuracy is set to prefer efficiency, but I almost always have night light on AND screen brightness/gamma lowered via kwin.

KWin Support Information:
The following information should be used when requesting support on e.g. https://discuss.kde.org.
It provides information about the currently running instance, which options are used,
what OpenGL driver and which effects are running.
Please post the information provided underneath this introductory text to a paste bin service
like https://paste.kde.org instead of pasting into support threads.

==========================

Version
=======
KWin version: 6.4.2
Qt Version: 6.9.1
Qt compile version: 6.9.1
XCB compile version: 1.17.0

Operation Mode: Wayland

Build Options
=============
KWIN_BUILD_DECORATIONS: yes
KWIN_BUILD_TABBOX: yes
KWIN_BUILD_ACTIVITIES: yes
HAVE_X11_XCB: yes

X11
===
Vendor: The X.Org Foundation
Vendor Release: 12401008
Protocol Version/Revision: 11/0
SHAPE: yes; Version: 0x11
RANDR: yes; Version: 0x14
Composite: yes; Version: 0x4
RENDER: yes; Version: 0xb
XFIXES: yes; Version: 0x50
SYNC: yes; Version: 0x31
RES: yes; Version: 0x12

Decoration
==========
Plugin: org.kde.klassy
Theme:
Plugin recommends border size: None
onAllDesktopsAvailable: false
alphaChannelSupported: true
closeOnDoubleClickOnMenu: false
decorationButtonsLeft: 0, 1
decorationButtonsRight: 3, 4, 5
borderSize: 0
gridUnit: 10
font: Noto Sans,10,-1,0,400,0,0,0,0,0,0,0,0,0,0,1
smallSpacing: 2
largeSpacing: 10

Output backend
==============
Name: DRM
Atomic Mode Setting on GPU 0: false

Cursor
======
themeName: BreezeX-Light
themeSize: 32

Options
=======
focusPolicy: ClickToFocus
xwaylandCrashPolicy: 1
xwaylandMaxCrashCount: 3
nextFocusPrefersMouse: false
clickRaise: true
autoRaise: false
autoRaiseInterval: 0
delayFocusInterval: 0
shadeHover: false
shadeHoverInterval: 250
separateScreenFocus: true
placement: 5
activationDesktopPolicy: SwitchToOtherDesktop
focusPolicyIsReasonable: true
borderSnapZone: 10
windowSnapZone: 10
centerSnapZone: 0
snapOnlyWhenOverlapping: false
edgeBarrier: 256
cornerBarrier: 1
rollOverDesktops: false
focusStealingPreventionLevel: 1
operationTitlebarDblClick: 5000
operationMaxButtonLeftClick: 5000
operationMaxButtonMiddleClick: 5015
operationMaxButtonRightClick: 5014
commandActiveTitlebar1: MouseRaise
commandActiveTitlebar2: MouseNothing
commandActiveTitlebar3: MouseOperationsMenu
commandInactiveTitlebar1: MouseActivateAndRaise
commandInactiveTitlebar2: MouseNothing
commandInactiveTitlebar3: MouseOperationsMenu
commandWindow1: MouseActivateRaiseOnReleaseAndPassClick
commandWindow2: MouseActivateAndPassClick
commandWindow3: MouseActivateAndPassClick
commandWindowWheel: MouseNothing
commandAll1: MouseUnrestrictedMove
commandAll2: MouseToggleRaiseAndLower
commandAll3: MouseUnrestrictedResize
keyCmdAllModKey: 16777250
doubleClickBorderToMaximize: true
condensedTitle: false
electricBorderMaximize: true
electricBorderTiling: true
electricBorderCornerRatio: 0.25
borderlessMaximizedWindows: false
killPingTimeout: 5000
compositingMode: 1
allowTearing: true
interactiveWindowMoveEnabled: true

Screen Edges
============
desktopSwitching: false
desktopSwitchingMovingClients: true
cursorPushBackDistance: 1x1
actionTopLeft: 0
actionTop: 0
actionTopRight: 0
actionRight: 0
actionBottomRight: 1
actionBottom: 0
actionBottomLeft: 5
actionLeft: 0

Screens
=======
Number of Screens: 1

Screen 0:
---------
Name: VGA-1
Enabled: 1
Geometry: 0,0,1280x1024
Physical size: 376x301mm
Scale: 1
Refresh Rate: 60020
Adaptive Sync: incapable

Compositing
===========
Compositing is active
Compositing Type: OpenGL
OpenGL vendor string: Mesa
OpenGL renderer string: AMD ARUBA (DRM 2.50.0 / 6.15.5-arch1-1, LLVM 20.1.7)
OpenGL version string: 4.5 (Core Profile) Mesa 25.1.5-arch1.1
OpenGL platform interface: EGL
OpenGL shading language version string: 4.50
Driver: Unknown
GPU class: Unknown
OpenGL version: 4.5
GLSL version: 4.50
Mesa version: 25.1.5
X server version: 1.24.1
Linux kernel version: 6.15.5
Direct rendering: Requires strict binding: no
Virtual Machine:  no
OpenGL 2 Shaders are used

Loaded Effects:
---------------
screenshot
outputlocator
colorpicker
zoom
screenedge
blur
logout
sessionquit
login
slidingpopups
windowaperture
slide
magiclamp
cube
kwin4_effect_geometry_change
frozenapp
scale
fadingpopups
dimscreen
dialogparent
wobblywindows
windowview
tileseditor
overview
highlightwindow
blendchanges
startupfeedback
systembell
screentransform
kscreen

Currently Active Effects:
-------------------------
blur

Effect Settings:
----------------
screenshot:

outputlocator:

colorpicker:

zoom:
zoomFactor: 1.2
mousePointer: 0
mouseTracking: 0
focusTrackingEnabled: false
textCaretTrackingEnabled: false
focusDelay: 350
moveFactor: 20
targetZoom: 1

screenedge:

blur:

logout:
pluginId: logout
isActiveFullScreenEffect: false

sessionquit:
pluginId: sessionquit
isActiveFullScreenEffect: false

login:
pluginId: login
isActiveFullScreenEffect: false

slidingpopups:
slideInDuration: 200
slideOutDuration: 200

windowaperture:
pluginId: windowaperture
isActiveFullScreenEffect: false

slide:
horizontalGap: 0
verticalGap: 0
slideBackground: true

magiclamp:

cube:
activeView:
delegate:
data:
configuration:
visible: false
activated: false
animationDuration: 200
mainDelegate:

kwin4_effect_geometry_change:
pluginId: kwin4_effect_geometry_change
isActiveFullScreenEffect: false

frozenapp:
pluginId: frozenapp
isActiveFullScreenEffect: false

scale:
pluginId: scale
isActiveFullScreenEffect: false

fadingpopups:
pluginId: fadingpopups
isActiveFullScreenEffect: false

dimscreen:
pluginId: dimscreen
isActiveFullScreenEffect: false

dialogparent:
pluginId: dialogparent
isActiveFullScreenEffect: false

wobblywindows:
stiffness: 0.15
drag: 0.8
moveFactor: 0.15
xTesselation: 20
yTesselation: 20
minVelocity: 0
maxVelocity: 1000
stopVelocity: 0.5
minAcceleration: 0
maxAcceleration: 1000
stopAcceleration: 0.5
moveWobble: true
resizeWobble: true

windowview:
activeView:
delegate:
animationDuration: 300
ignoreMinimized: false
mode: ModeAllDesktops
partialActivationFactor: 0
gestureInProgress: false
searchText:
selectedIds:

tileseditor:
activeView:
delegate:
animationDuration: 200

overview:
activeView:
delegate:
animationDuration: 300
ignoreMinimized: false
filterWindows: true
organizedGrid: true
overviewPartialActivationFactor: 0
overviewGestureInProgress: false
transitionPartialActivationFactor: 0
transitionGestureInProgress: false
gridPartialActivationFactor: 0
gridGestureInProgress: false
desktopOffset:
searchText:

highlightwindow:

blendchanges:

startupfeedback:
type: 1

systembell:

screentransform:

kscreen:


Loaded Plugins:
---------------
BounceKeysPlugin
KeyNotificationPlugin
MouseKeysPlugin
StickyKeysPlugin
TouchpadShortcutsPlugin
buttonsrebind
eis
krunnerintegration
nightlight
screencast

Available Plugins:
------------------
BounceKeysPlugin
KeyNotificationPlugin
MouseKeysPlugin
StickyKeysPlugin
TouchpadShortcutsPlugin
buttonsrebind
eis
krunnerintegration
nightlight
screencast

I did some inspection with radeontop and merely using the Zoom effect bumps graphics pipe utilization by ~30% alone, this adds up with other composite heavy windows on-screen and begins reducing FPS below the screen's refresh rate. I've done a comparison with the Magnifier effect and magnifier seems to use a negligible amount of graphic compute by default, only around 5%. it can go up to +20% if the magnifier size is set to 1024x1024+.