Wanted to post this here in case someone comes across this issue.
When I first installed the Xfce (ultimate, but shouldn't matter) there was a mild flicker, which is not uncommon when using compositing window managers with NVIDIA cards.
The fix for it in my experience, has always been to create a xorg.conf file to force to use the compositing pipeline. There are many approaches to do this, but easiest one is using nvidia-xconfig or nvidia-settings, but you can manually create or edit the Xorg.conf file too.
- nvidia-xconfig offers these compositing configuration options:
❯ nvidia-xconfig -A | grep "composition\|\[options\]" -C1
nvidia-xconfig [options]
--allow-glx-with-composite, --no-allow-glx-with-composite
Enable or disable the "AllowGLXWithComposite" X configuration option.
--composite, --no-composite
Enable or disable the "Composite" X extension.
--damage-events, --no-damage-events
Use OS-level events to notify the X server when a direct-rendering client has performed rendering that needs to be composited to the screen. Improves performance when using GLX with the composite extension.
--force-composition-pipeline=FORCE-COMPOSITION-PIPELINE, --no-force-composition-pipeline
Enable or disable the "ForceCompositionPipeline" X configuration option.
--force-full-composition-pipeline=FORCE-FULL-COMPOSITION-PIPELINE, --no-force-full-composition-pipeline
Enable or disable the "ForceFullCompositionPipeline" X configuration option.
In my experience, simply enabling the below is enough, but I welcome you to try some different settings and share with the rest of us:
$ nvidia-xconfig --force-composition-pipeline=FORCE-COMPOSITION-PIPELINE
-
nvidia-xsettings(to save the Xorg file you may need to run as sudo)
In either scenario, the Arch Linux wiki Nvidia Article recommends saving the configuration file at /etc/X11/xorg.conf.d/20-nvidia.conf, but simply saving at /etc/X11/nvidia.conf is also enough.
The effective file will contain the lines similar to (this is not a complete configuration, merely an excerpt):
Section "Screen"
Identifier "Screen0"
Device "Device0"
Monitor "Monitor0"
DefaultDepth 24
Option "metamodes" "1920x1080_144 +0+0 {ForceCompositionPipeline=On}"
EndSection
Not that is wholly applicable to this case, here is a copy of my:
/etc/X11/xorg.conf.d/20-nvidia.conf
I'm not the most well versed in the complexities of compositing, but even if not optimal, it worked for me, and while I would love to figure out if this is the best solution, I thought it could help anyone seeing this issue. 
