Emerging markets are getting energized this year.

The most well-known emerging markets exchange-traded fund, the EEM MSCI ETF, has rallied more than 11 percent in 2019, keeping it at the heels of the S&P 500's nearly 13 percent gain. The VWO Vanguard FTSE emerging markets ETF and small cap-focused IEMG MSCI emerging markets ETF, which holds small caps, have had similar moves this year.

Tom Lydon, editor-in-chief of ETFTrends.com, said there's is an important question to ask when deciding upon how to play the emerging market.

"Recently it's been all about China and China does make up a big part of emerging markets today," Lydon said on CNBC's "ETF Edge" on Monday. "Do you want to play all emerging markets or do you want to be specific on China? There are a lot of varieties out there."

The EEM ETF, for example, has 73 percent exposure to the Asia Pacific with 23 percent coming from Hong Kong, 10 percent from Taiwan, and 8 percent from China.

Lydon says a better way to gain exposure to the China space is the ASHR China A-shares ETF, a more-focused mainland China play. It has rallied more than 30 percent this year.

Todd Rosenbluth, director of ETF and mutual fund research at CFRA, says investors need to be aware of what is in their emerging markets ETF and whether they have enough, or any, exposure to their favored region.

"You really need to look under the hoods with ETFs, and emerging markets are a perfect example of that," Rosenbluth said on "ETF Edge on Monday. "EEM, and a cheaper version IEMG, has South Korean exposure – it's about 14 percent of the portfolio. VWO does not have that so it has more exposure to India, South Africa, other countries besides China."

Investors can play an even more bullish bet on the emerging markets by pairing a long position with a short position on the developed markets. The Direxion RWED emerging over developed markets ETF, for example, is 150 percent in emerging markets and 50 percent short the developed markets.

"Investors can be tactical using ETFs whether they are focused only on emerging markets or if they want to do that relative to developed markets and these Direxion products are new but are very compelling to take a look at," said Rosenbluth.

Direxion also has a long developed markets, short emerging markets play in the RWDE ETF. Both launched earlier this year.