The second bucket can be invested in a combination of income and growth assets. How best to get income from investments in retirement is a problem that has many possible solutions.
The return on an investment portfolio is a combination of income (interest or dividends) and capital gain (the increase in the value of the investments over time).
The disadvantage of income-producing investments is that the income is taxable and in general they offer little or no capital gain and a low return.
The disadvantage of growth investments, which offer capital gain and higher returns over the long term, is volatility, and to get cash you may have to sell investments at a time when their value is down.
Running down investment capital is another issue. Some investors wish to leave a sizeable inheritance while others don't; some are wary of running down capital in the early stages in case large sums are required later.