Need for Speed: Unbound has an unsupported status on Steam Deck, but after setting Proton Experimental, the game works fine! I haven’t had a chance to play longer yet, but at first glance the whole production is very playable on Steam Deck.
NFS: Unbound has a lot of graphics options, including support for AMD FSR 2.1 scaling, but even on the lowest settings it has minor performance issues. Valve has not yet prepared a shader cache for this game, so for the first minutes of gameplay the stuttering is annoying, but after a while you can see an improvement in fluidity.
I think the 40FPS limit is achievable for Need for Speed: Unbound, but I have yet to test it closely. I will publish optimized settings for this game soon.