What really matters in this, imho:

• prompt quality and completeness. Everything you won't specify will be hallucinated
• the amount of work you're willing to put into questioning replies. This may be the most important of all.
• scope. Scope too narrow, you get bullshit results. Scope too wide, you get bullshit results.
• sub-agent/task decomposition. You have to instruct this correctly or you'll have re-scoping in sub-agents
• error correction. Any "reasoning" error that doesn't get fixed compounds. You have to get your errors out quickly.

I suggest you try it on one of your firmware codebases. You'll have fun.