I'm not as familiar with the Astros as the Nats, but I'll give it my best shot. You can probably find good summaries on the Internet.
Astros
First three starting pitchers: Cole, Verlander and Grienke
Altuve -- one of the smallest if not the smallest active player in MLB (5' 6"). Despite his diminutive size, he has no trouble hitting home runs and exactly at the right time.
Nationals
First four starting pitchers: Scherzer, Strasburg, Corbin (though he may be a relief pitcher in the first two games) and Sanchez
Rendon -- strong defense at third base and is having a career year at the plate
Turner -- strong defense at shortstop. I call him Afterburner Turner. One of the fastest in baseball. If he gets on base and tries to steal, he'll probably be safe. He makes baseball fun.
Soto -- average defense in left field. He turns 21 during the World Series and set a bunch of records for 19 and 20 year olds that put him in the elite of all-time young baseball greats
Kendrick -- utility player who will be the pinch hitter when playing in Houston. Regular season batting average close to .350 and doing great in the playoffs
Overall
The pitching match ups are being hailed as those for the ages. Watch for great starting pitching by both teams.
Every prediction I've seen except one is that the series will go six or seven games, so the series has the potential to be a nail-biter for both teams and their fans.
Each game could be won by one bad pitch that becomes a home run. Both teams have an ample supply of home run hitters.
Nationals are the oldest team in MLB; look for what the old guys are capable of doing.
Nationals have had a week off since playing their last game. Astros have had a few days off. Look for symptoms of advantages and disadvantages about that for both teams.