> what do they do with it, and how does effect the economy compared to the way lower wealth people behave when they receive money?

Most of the wealth of the top 1% (to pick an arbitrary "small group of people") is not sitting as cash in the bank; it is concentrated in financial and business assets: equities & mutual funds, private businesses, real estate, bonds and other fixed-income investments, alternative assets.

In the US, over half of all publicly traded stocks and mutual fund shared are held by the top 1%, meaning their wealth is overwhelmingly tied to ownership of productive assets rather than wages or savings accounts (and is therefore illiquid).