Is wholesale banking same as investment banking? Or are investment banking and commercial banking a subset of wholesale banking?
Um. This is sort of tricky, since none of those terms really have a defined meaning, and they can even vary between banks.
"Wholesale" and "Commercial" banking are both pretty fuzzy terms, but I'd say "commercial" banking refers to services for companies, rather than individuals; and "wholesale" refers to banking refers to services for other intermediary institutions (since you're 'wholesaling' the banking services). These are both just guesses, though.
"Investment banking" is slightly more defined; usually that refers to the M&A and IPO & capital markets functions. Sometimes it covers sales-and-trading as well (it did when I was at ANZ—the sales and trading functions were part of "ANZ Investment Bank"—but not sure if this still applies).
the key question is which can reduce my risk and increase my returns
which ever can do that, that's the good one
Do us all a favour mate: stick to the questions where you have something useful to contribute.