Can I run Hy3 on a Mac with 128 GB?

No

Even its smallest file (4-bit (estimate), 168 GB) is more than a Mac with 128 GB can hold (96.0 GB usable): it needs a Mac with 256 GB.

Files and context on Mac with 128 GB

Each file of Hy3 (and of GGUF versions the site has analyzed), and how much context fits next to it, with the context cache in 16-bit or 8-bit.

Hy3 on other hardware

Popular models that run on Mac with 128 GB

Assumes 75% of the Mac's memory is usable (macOS's default limit for the GPU; it can be raised) and at least 4K tokens of context for one conversation, with the context cache in 16-bit unless noted. Fits leaves at least 20% of that memory for context; Tight leaves less.