My take:

Large: Requires >128GB VRAM

Medium: 32-128GB VRAM

Small: 16GB VRAM

Micro: Runs on a microcontroller or GPUs with just 4GB of VRAM

There's really nothing worthwhile for general use cases that runs in under 16GB (from my testing) except a grammar-checking model that I can't remember the name of at the moment.

gpt-oss:20b runs on 16GB of VRAM and it's actually quite good (for coding, at least)! Especially with Python.

Prediction: The day that your average gaming PC comes with 128GB of VRAM is the day developers will stop bothering with cloud-based AI services. gpt-oss:120b is nearly as good as gpt5 and we're still at the beginning of the AI revolution.