If you try to run any new AAA title on any current handheld you're going to have a bad time and bad battery life IMO. I think you could even extend this to modestly old gaming rigs that already struggle badly with poorly optimised new titles.

I see the Deck praised often for its emulation capabilities and indie game performance - and to be honest those aspects are appealing enough to me if I was interested in buying another portable computer.

This is the new Steam Link

Out of curiosity, what makes you think this?

I doubt this is the case as thin client gaming accessories are a very niche product, and the Deck hardware is grossly overqualified in this regard IMO