If both of the Decks connect to the same WiFi, you’d be able to play local multiplayer games just fine. Not every game will support local multiplayer though, and vice versa.

As for games: How about Divinity Original Sin 2? Plenty of tactics, but also a lot of reading. Has local co-op support, but the fights are turn based anyway so I’m sure what latency issues you had over L4D2 wouldn’t be a concern.