Corrections happen. Crashes happen. No one can predict them. What you're talking about is market timing, and that never ever ever works. If you're in the market long term, then you'll see lots of that over time, but the market will trend upwards. Last year was a super year, but that doesn't mean that there is no where to go but down now. Even if we do end up with a correction this year, it will only effect you short term. And if you are dollar cost averaging money in, then if the market is down, you're getting the fund "on sale."
I don't know much about the fund you're looking at other than a quick skim of the Vanguard page, but it is a high risk/high return fund, and that means it will be a roller coaster ride. As far as tax efficiency, if it has low turnover, that is one of the signs it is more tax efficient, and this one has a 10.9% turnover rate so it seems decent.