Are you mining to a wallet or an exchange?
What is the reason to send to btc and then another btc address?
Yes, there are transaction fee's involved so you must account for those when sending to different address.
I mine under one address on an exchange there are no charges involved for this, only pool side fee's.
My advise is to keep to one address.
I am mining to a freewallet.org wallet. Then I sent ZEC to BTC. And now I would like to send BTC to poloniex BTC account. Is better to mine to poloniex address or leave ZEC in the wallet and send when I will have higher amount ? I do not known diference between mining to wallet and to exchange. Mining to wallet is freewallet.org and mining to exchange is poloniex ? Thank you.