Firefox webrender pi4/400

Relevant system info

OS: Manjaro ARM Linux aarch64
Host: Raspberry Pi 400 Rev 1.0
Kernel: 5.11.15-1-MANJARO-ARM
WM: sway
OpenGL: renderer: V3D 4.2 v: 2.1 Mesa 21.2.0-devel (git-c74d93cf01) 

$ cat /boot/config.txt | grep dtoverlay

$ cat .zprofile
if [ "$(tty)" = "/dev/tty1" ] ; then
    export QT_QPA_PLATFORM=wayland
    export GDK_BACKEND=wayland
    export MOZ_WEBRENDER=1
    export PAN_MESA_DEBUG=gl3
    export XDG_SESSION_TYPE=wayland
    export XDG_CURRENT_DESKTOP=sway
    exec sway

doing a fresh install of manjaro with the 21.04 manjaro minimal image and I’m setting up a sway environment. I’ve completely forgot what to tweak to improve firefox performance and googling around I found this thread from on the forum: Firefox WebRender

so I decide to go with gfx.webrender.all & gfx.webrender.enabled as well as setting the env variable export PAN_MESA_DEBUG=gl3. This indeed does result in great performance with the Chalkboard HTML5 Benchmark, but other than that the browser runs poorly and causes pages to glitch out – for example, about:support will not display properly, constantly blinking in and out as I scroll the page, with this issue repeating itself on other pages. Additionally, another website I like to use as a makeshift benchmark, fallingfalling, runs poorly as well. I can get the browser in working order if I change in about:config layers.acceleration.disabled to true but then the html5 benchmark scores poorly.

Am I overlooking something that’s keeping me from using WebRender in firefox and having the browser function properly? Thanks for any help and suggestions.

Hi !
Which add-ons ?

grep -oP '},"name":"\K[^"]+' ~/.mozilla/firefox/*.*default*/addons.json

it’s a fresh install so I have no addons on the browser currently:

$ cat ./addons.json

WebRender in ARM is still pretty hit’n’miss. For some devices/usecases it’s great, for some not so much.
Personally I don’t change the default, and my browser performance is okay on my Odroid N2+.
Sure, it’s not as fast as my Ryzen 2700 desktops Firefox, but I have no assumption it ever will be.

I kinda had a feeling. Yeah, the browser performance is not bad at all considering the device. Just wanted to double check.