So, yesterday I installed i3-gap with my KDE DE but when I tried bspwm & Qtile it booted with the black screen & only my mouse was visible on the screen. Is other WM are dead in Manjaro?
You are probably missing the necessary configuration files.
You will have to create them by hand or search for some to get started.
While you can assemble a Linux system out of anything you like - not every piece are meant to work together or you may have trouble getting them to play nice.