What’s your best LLM workflow for planning vs execution?

What’s your best LLM workflow for planning vs execution? When building things like apps, websites, designs, PDFs, or learning docs: Which model do you use to plan? Which model do you use to execute? Do you split planning and coding/building across different models? For coding, do you use Codex, Claude Code, or something else? Does your workflow change by task type? I feel like planning is the most important part, so I want to know which model is strongest at planning, and which is strongest at doing. Would love to see your actual workflow step by step, not just model names.