Neither. None of the players you mentioned are good enough to fill Nik's shoes - Kakko has done f*** all in some very generous deployment next to Panarin and co., Chytil may or may not be fit to play hockey, and Laine doesn't do anything that you'd want from an Ehlers replacement (and may not be healthy either).
If there was a RW who I'd absolutely love to see us get, it would be Alex Tuch. Since everyone else is taking the Sabres to the cleaners, I'd be thrilled to see us join in and get an actual top 6 RW with a versatile set of skills. He's a top 30 point producer at 5v5 across the last three seasons, too. That's a guy who you could talk about as an adequate Ehlers replacement, and if he'd be open to re-signing, he's also 110% worth sending Rutger over in a trade.