While goaltending has been an area to improve in 5-on-5 play, it's been top ten in the NHL this season when it comes to penalty killing. Add on top of that that the Kraken take the fewest penalties per game of any team in the league, and we see how Seattle has been able to keep opponents' power plays completely off the scoreboard in seven of their last eight games.
As for the power play, while it took a while for the team to find the goals, the groupings have been doing the right things all season. The Kraken currently rank second overall in terms of power play shot quality (per Evolving-Hockey.com), and they rarely give up shorthanded opportunities with the lowest shot quality against.
What may have been fighting Seattle early in terms of seeing power play results is, in part, the dreaded "puck luck." On the season as a whole, the Kraken have the 18th best shooting percentage when playing with the man advantage. If you are doing the underlying things right (like getting the shot quality), you can expect that finishing ability to, at the very least, get up to league average.