I haven't understood a bit from it, but I guess I never dig so dip on how it works or why this stuff is so different on Manjaro.
Anyway, I had basic mhwd non-free bumblebee setup (intel/nvidia) and this gave me all I needed.
My experience is: people who mess with graphics packages manually have issue after issue and are massively confused, what to install, what to not install, what to blacklist, etc. Mhwd works well for most.
Too bad that in OPs case non-free mwhd setup has an issue of the starting X session. On another hand, all optimus-manager installation and configuration can be done from tty and there is a chance that it will fix any issue it was in the first place and system will boot correctly into intel session (by default).
Or, he (the OP) can just install proprietary drivers via mhwd and do all the configuration from working X session (so before reboot) and then try to reboot to see if it works. So I guess there is a potential there.
I already started with the optimus-manager tutorial and it's possible I'll finish it tomorrow, but as I said, it assumes working mhwd bumblebee non-free setup (on a hybryd GPUs). If someone messed with the packages manually (install this or uninstall that), then there is a high chance that it won't work. So as a rule of thumb, any newbie user should stay away from any manual driver configuration and relay on mhwd (if it's possible).
@dglt, of course I welcome to improve the tutorial once I posted it. I assume, that you have the rights to edit topics/posts in tutorial section?
I believe that optimus-manager matured enough to be presented to the wider public and people are too scared of it. It's not that complicated, although the original Install section on github is not written in a optimal way (and thus confuses newbies) so I intend to change it.