You asked
Is the leica q3 monochrom worth it?
The Leica Q3 Monochrom is worth it only if you shoot black and white almost all the time. It has the same 60-megapixel full-frame sensor and built-in 28mm f/1.7 lens as the Leica Q3, but it records only monochrome. If you still want colour now and then, the regular Q3 covers both.
If you prefer a different view, the Leica Q3 43 swaps the 28mm for a 43mm f/2 lens. Before you commit to full frame at all, read Is full frame worth it?. It's a yes for low light and shallow-depth portraits, but for travel and street, a good APS-C camera is often enough and easier to carry.
Written by Claude from this site's pages.