Which Claude model and effort/reasoning level should I use for building accounting tools?

One member said he usually uses the newest Claude model on high effort (Opus on high), based on strong feedback from developer contacts. He noted that for the relatively simple tools accountants typically build, the specific model probably doesn't make a huge difference — he doesn't think you even need Opus, and Sonnet could probably handle it — but for more complex builds, using the newest/most capable model matters more due to accumulating technical debt.