Fresh updated install of Manjaro KDE sometimes not loading some user preferences

Been having problems on my "old" Manjaro KDE install, decided to finally reinstall and the problems are still there. Basically, I install the latest image of Manjaro KDE (wiping the full disk), reboot, do a sudo pacman -Syyuu, reboot, install latest kernel, reboot, set touchpad acceleration settings and reboot. When I log in, the mouse moves with the same slow speed as on the log in screen and parts of the theme switch to Breeze Dark. This does not always happen, but quite often as it already did so twice in a row after my latest reinstall. Currently on Manjaro XFCE because of this bug but I'll gladly reinstall the KDE spin again if the problem can be solved. Any help is appreciated!

Are you re-using a /home folder? If so, try creating a new user.

Nope, I'm wiping the full disk, not copying anything back at that point. All the modifications I do are only what I listed above and all are done through KDE's settings GUI. (Expect the initial update as I've had problems with Octopi not allowing downgrades once.)

So which theme did you set?

Haven't manually set one, so it was the default light theme that came with it during install.

But parts sometimes display as breeze dark? Screenshot may help.

Exactly. The bottom panel was dark while the rest of the GUI was light. Will reinstall and provide screenshots tomorrow.
Oh, and most importantly, thanks for all the help so far, this community is already much more welcoming and responsive than Microsoft's Support Forum where they just tell you to do an sfc scannow, mark your question as solved and move on.

Install kde on top of xfce, they co-exist well.

sudo pacman -S plasma kf5

Select from your desktop manager.

Alright, did it. Theme is remembered just fine this time but my mouse is slow again and tap to click doesn't work. Despite this, KDE Touchpad Settings GUI shows the values I set previously. Logging into XFCE is fine and my settings are respected there.

I don't like libinput, but it is the future :face_with_hand_over_mouth:

I use a touchpad and I tried to change the acceleration and it did diddly squat.

Sometimes it works, sometimes it doesn't. Is there a config file I could edit directly? Tried touchpadrc but that did nothing but get overwritten by the values in the GUI.

Don't think so.

Alright, it seems I've fixed it by downgrading the kernel from 5.1.8-1 to 5.0.21-1. I wonder what goes wrong on the newer kernel...