I’ve now installed/enabled the video-modesetting driver from Manjaro Settings GUI on the alternative account based on suggestions made in this post - How to use the modesetting driver? and rebooted.
An interesting development - after the spinning wheel post-login (into the faulty original profile, not the alternative used to set-up modesetting driver), I got the usual black screen w/cursor on my Display 1 (laptop). However, one half of the Display 2 screen (work monitor, hooked in through Mini DP port) I was greeted with a stock wallpaper and kded5 + kdewallet apps requesting a password!
Which I absolutely did not touch at all since installing Manjaro!
I pressed cancel and it defaulted back to the black screen. I stopped the GUI session via tty and rebooted again. Same thing.