I bought Lethal and Fruit Ninja for PSVR. My thoughts on the two games:

Lethal:
It's a shooting gallery with 30ish challenges where you chase for a higher score, and compare it on a worldwide leaderboard. Gameplay wise it's OK....except for the knife throwing parts. There's a certain range in which you can throw your knives before the tracking gets wonky. Shooting guns however is awesome! Protip: you need to imagine yourself firing a real gun in a gun range. Hold a move controller with both hands, aim down the sights. Shooting best practices will definitely help you score them headshots!

Fruit Ninja:
Don't get turned off because it's from a mobile title, coz there's nothing like this AFAIK for PSVR. You're given 2 katanas, the 4 standard modes, and NEAR 1:1 MOVE TRACKING FOR YOUR FRUIT SLASHING. The moment my slash connects with a fruit, the vibration from my controllers almost convinced me it's real. You can even bounce the bombs on your swords for a bit! It's fun, but in short bursts because your arms will get tired from playing.

Ultimately these two games are score chasers. No real depth to them but replayability is what they do best. It's a buy, but not exactly a must buy. Get them if you want to convince people the virtues of PSVR (or you wanna make use of your Move controllers that have been collecting dust lol)

Personally, Thumper is still my #1, must buy must play PSVR game tho. There's nothing else like it.

Play 2D games in PSVR or just TV screen?

Either way, you don't need to disconnect anything. Just play any game you want as usual.