It really depends on what your needs are, but for 2D graphic design, the M1 is more than capable. I run the Affinity suite on it (Designer, Publisher, and Photo) which are roughly equivalent to Adobe CC apps and I've never noticed any slowdowns or issues. Even using browser-based design apps like Figma and tools like Miro run pretty snappily (even with very large, very complex boards).
If you're doing print publication design (InDesign style stuff) or photo editing and 2D illustration (Illustrator, or various paint programs etc) I would say spring for the 16GB model just to be on the safe side when working on very large files. And get decent fast external storage for files and backups.
Regarding monitors etc, the Mini can support 4K and 5K monitors easily. No problems with a dual monitor setup.
If you wanted to go into 3D design work or 3D animation, it can handle a good deal of stuff in the wireframe mode etc, but would be slower than a dedicated 3D graphics workstation. An M1 Max laptop might be better for that right this second, but as others have said, maybe wait to see if there are any product refreshes in the Spring.