Step one remove plymouth - make notes in case you later want to revert
→ [HowTo] Disable or Remove Plymouth (boot splash)
Step two
Check the configuration of kernel mode settting.
As disabling modesetting gives you image on screen it could be related to the default of enabling kms in mkinitcpio.conf.
→ Black Screen with Plymouth - Cause and Solution - #2 by linux-aarhus
So I’d say remove quiet, splash from kernel cmdline in grub - and kms from mkinitcpio.conf HOOKS and - if you added it - i915 - from mkinitcpio MODULES.
i7-6700K - this is a desktop CPU right ? not a dual GPU laptop ?