Not sure, but if the controller is gone it should be fine. I still have the nouveau.conf file, so I don’t think they really matter once the driver is gone.
The only thing I can think of being in the way is the Grub flags at startup. Can you check how the line
GRUB_CMDLINE_LINUXlooks in your file
/etc/default/grub? Sometimes you have to play with those flags to get the jackpot combination.
And, as @just says, I would not try to use prime: I was never able to make it work reliably in my setup. Your mileage may vary, though.
That is weird, yesterday I was able to install bumblebee in an XPS15 (with a GTX1050M) and following the guide worked wonderfully in KDE (actually better than my previous attempt with Ubuntu and Gnome). Honestly, I am quite a noob in this topic, but you seem to be blacklisting nouveau: is there a reason to do this? The guide actually suggests to completely remove it (
sudo pacman -Rc xf86-video-nouveau) so it should not be necessary to keep blacklisting it or disabling it in the Grub settings.