50B+ MoEs with few active parameters, what's the sweet spot for intelligence, agent speed, and affordable fine-tuning?

I’m building a Polish General purpose legal Model that drafts documents, answers questions using legal sources, and has enough coding ability to handle some automation. The workflow is very tool-heavy:

Question → many sequential tool calls → final answer/document

Think Claude Code/Codex-style execution, but for legal workflows. Reliable tool selection, correct arguments, and recovering from errors matter as much as writing a good final answer.

I’ve had decent results with a dense 27B Qwen 3.8 custom made fine-tune for complex legal document summarization and classification. I’m already familiar with the smaller Qwen A3B and Gemma options. What interests me is the tier above those: 50B+ total-parameter MoEs with a relatively small active parameter count.

The question is, the small dense ones are great, but slow for agentic stuff (afaik), and i wonder if theres some middle ground maybe 70-120B models that would be able to be fine-tuned for the law stuff but be MoE so the agentic ClaudeCode style inference would also be lightning fast, and also low-ish cost for fine-tuning and inference.

Basically: Does the larger-total/small-active MoE approach actually buy you meaningfully stronger reasoning and tool reliability while retaining low latency,and at what hardware cost?

I understand that small active parameter counts don’t mean small VRAM requirements: the weights still need to live somewhere, alongside context and serving overhead. I also don’t assume that more total parameters automatically means a better model. I’m interested in where that tradeoff works in practice .

There are three things I’m trying to pin down:

- Inference hardware: Ideally inference runs rented with parallel agentic loops (this is for a B2C project, not single person use, we scale based on demand)

- Fine-tuning hardware: Obviously FT LoRA will take more memory than inference, max like 4GPUs on vastai fits the budget.

- Agent performance: After it gets the prompt the tool calls and everything will be local, so imo it has no problems being blazing fast, as soon as the model calls a tool call it will be back very fast, so for this agentic use case, quick TTFT and t/s and adaptive dynamic reasoning are prefer right?

For context, fine-tuning would target Polish language, document conventions, and successful tool trajectories. The actual legal sources would remain in retrieval/tools rather than relying entirely on memorized law.

I’m not looking for someone to compile a model shortlist (althought would be nice, but i dont expect anyone to break their back over this).

I’m looking for pointers, and firsthand experience with this particular size/architecture tradeoff. A configuration like “model + quantization + GPU(s) + serving engine + context length + concurrency + measured latency,” along with whether you successfully fine-tuned it, would be much more useful than a leaderboard score.

Has moving from a ~30B model to a 50B+ low-active-parameter MoE actually improved your agent’s successful tasks per minute, or did the memory, interconnect, and training requirements erase the advantage? Thanks for reading