Expenditure method - ignore intermediate transactions and only count the final expenditure on national product.
Output method (production method, industry of orign method) - value added. Final expenditure cann be broken down to show the industry of orign
Income method - factors of production. Completely other from previous 2 and helps a lot to compare. Easy to calculate from the income tax receipts.
Wages and profits reach household sector from productive secotr and private consumption is returned. Value added measures the flow that leaves productive sector, national income measures the amount received by households and final demand, or expenditure is the amount reaching the productive sector again.
The data is not meant for national income accounting, but for paying tax, import duties etc.