I installed the Plasma Testing ISO on my optimus laptop as well as the appropriate Nvidia drivers, and a reboot has left me with a black screen. This is different from the nomodeset problem as I do not have to use that kernel parameter with Budgie/LightDM and using it anyway did not solve the problem. This is an issue specific to the Plasma install, not Budgie.
Uninstalling the Nvidia drivers gives me a working system - presumably using the Intel card - so I'm still able to use my laptop, just not for gaming.
Attached is an Xorg log file from trying to get an X session with the Nvidia drivers.
I have a Skylake i5 processor (Intel HD Graphics 530) and an Nvidia GeForce GTX 950M.
As a side note, is bbswitch-current necessary to be able to use the Nvidia driver? It was not preinstalled on the image nor was it installed when I installed the drivers through DoFlicky.