Finally...

An 32/64 bit compatible Quartz Composer composition compatible screensaver for MacOS Mojave!
Build script is available here if you're not familiar with XCode

But thats not all!

It also has an interactive mode by default,
so you can do stuff with compositions at fullscreen with mouse and keyboard interaction!
With this it doubles as a viewing application for your 32bit and 64bit compositions on Mojave 10.14.6 <3

Shame this wasn't a option all along, but here we are.

Command-line Flags:

Note: you can put these flags in the QCRunner.app/Contents/MacOS/QCRunner.flags file for default settings.
Anytime you edit this file you'll probably have to re-toggle QCRunner in the Accesibility window that pops up.

--debug
Enables verbose logging to console.

• Default: off.

--comp <path> or --comp=<path>
Path to the .qtz composition to load. Relative paths are resolved relative to the executable’s directory.

• Default: if omitted, it tries to load Default.qtz from the app bundle; if that fails, the app alerts and (in interactive mode) quits.

--screensaver <seconds> or --screensaver=<seconds>
Enable saver mode. Shows the composition only after Quartz reports continuous idle for the given number of seconds; hides the cursor while showing; any mouse activity dismisses it.

• Alias: --ss / --ss=.
• If you pass 0 or a non-positive value, it falls back to 300s. Default: disabled (interactive mode).

--ss-keys
In saver mode, also dismiss on any key (not just mouse). Uses a local key monitor and, if permitted, a global CGEvent tap (Accessibility permission).

• Default: off.

--any-key
In interactive mode, any key will quit the app (otherwise only Esc or Cmd+Q quit).

• Default: off.

--quit-on-mouse
In interactive mode, any mouse movement/click/scroll quits the app.

• Default: off.

--auto-quit <seconds> or --auto-quit=<seconds>
In interactive mode, auto-quit after the specified number of seconds.

• Default: disabled.

Force 32bit or 64bit Architecture:

32 Bit: arch -i386 QCRunner.app/Contents/MacOS/QCRunner --comp stuff.qtz
64 Bit: arch -x86_64 QCRunner.app/Contents/MacOS/QCRunner --comp stuff.qtz

You can also create a 32bit ONLY copy of the app via:
ditto --arch i386 "/Applications/QCRunner.app" "/Applications/QCRunner (32bit).app"

Important note:

Before running the app, Please go to
System Preferences > Security & Privacy > Accesibility > ... And then add QCRunner here.
It needs this permission to be able to read mouse/keyboard input.
If you are using a quartz composition that uses camera or microphone input,
and for some reason your system does not request permission, try using this script
I made to manually force these permissions for any application.

To Run at Login

Simply go to System Preferences > Users & Gropus > Login Items > + ... and add QCRunner