The change wallet address will just give you a different BTC address to send your BTC to. It won't do any harm, but there is no real benefit to doing it unless you want different transactions to be tracked on the bitcoin chain with different wallets. Most users have no reason to do this.
I'm not sure about destTag. Where do you see it? If possible, can you send a screenshot?
Hello tim and thank you for this tutorial, so is buying bitcoin the only way to buy steempower?
There are also options to buy with Ether or Bitshares.
Thanks Tim