For investment and for transactions, crypto coins have both and can indeed be used together.
But seeing the fast progress of cryptocurrency, you need to be careful in investing, it's easier to invest with coins that are already popular and trustworthy like on the CMC list.
For payment transactions, you can use a choice of altcoins that already have an exchange or stable coins that you can choose, if you only want to use them for payments, you don't need to worry that the value of your altcoins will drop because the price of crypto coins fluctuates.