nwchem VS xtb

I still use VMD sometimes but I don't use GAMESS anymore. It is a bit difficult to make recommendations without knowing your knowledge level and the operating system that you are using. If you are comfortable with Python, you could start with Psi4. If you know how to compile programs you can try building and running NWChem. Orca is also popular but I have not used it myself. If you are at a university you may have access to other proprietary quantum chemistry programs such as Gaussian or ADF. You can choose any of the programs available to you, and then follow the tutorials and examples in the manual. Once you understand the basics it is easy to learn how to use any program as they all share common features.

Yes, it works. See https://github.com/nwchemgit/nwchem/issues/320 and https://github.com/nwchemgit/nwchem/pull/326. I am an NWChem developer and M1 owner.

Okay, so I have no direct experience with the M1 and its specific feature set, but NWC does run with arm devices so it should not be problem (here is a link to compile on a mac MacOSNWChem . Also NWC is Open Sauce so just grab a copy and try it out.

Have you tried using GFN2-xTB (https://github.com/grimme-lab/xtb)? It is essentially the fastest method you could use, after forcefields, but is designed as general-purpose tool. I haven't tested it with Zn, but it's worth a try.

I would recommend getting xtb (https://github.com/grimme-lab/xtb) and exploring some possibilities. The calculations are lightning-fast, so you have a quick feedback loop and you can quickly test different ideas. You can look at recent publications to get an idea of what people are doing.

the xtb and dftb programs are actually excellent example of well-written, clear, modern fortran codes. I've learned more from reading these codes than from any other resources.