CNBC's Frank Holland spoke with Dave Nadig, Director of Research at ETF Trends, Jay Rhame, CEO of Reaves Asset Management, and Kathleen Smith, Chairman and Co-founder of Renaissance Capital. They discussed the big questions ETF investors are facing in the second half - including the value vs. growth debate, how China's regulatory crackdown could affect major IPOs like Didi Chuxing, and the ripple effects of President Joe Biden's historic infrastructure bill.