Hi, is it worth having an iPhone and Android at the same time?

I'd like to buy an Android for WhatsApp. I don't want to use my iPhone nor my real number for WhatsApp. This may seem silly, but this is due to my privacy with my family and close friends that when I chat in WhatsApp for educational purposes, I will have a separate one particularly for that. Do I need a different phone number? Do I need a different SIM memory? Is it possible for a single person to have two phone numbers (to hold them?) or do I have to keep my original or let one go? How does this all work? If I get the money, I'll buy myself an extra phone for WhatsApp group chat purposes BUT on Android. Should it be the LATEST edition Android phone and what phones are Android-specifically? Do I have to pay a separate phone company that isn't the same line on my iPhone, if I get an Android phone? For example, I'm using T-Mobile. Does that mean I need to get AT&T or Verizon or something else? Thanks!!!