I have a shield.
It is a android tv device that uses powerful nvidia hardware similar to that used in a Nintendo Switch. in fact it is about the same size. and is really intended as a strange android console contender.
it comes with fantastic xinput joypads and many android developers make specific high spec versions of their apks for shield that can use the extra hardware and joypad.
as it is android it will run apks and it will run games through the browser.
it is also specifically designed to be used for various game streaming services including, what you are talking about, steam link, which is streaming games over a local network using steam from PCs that have nvidia graphics cards ( i think they need to be gforce/gtx) in a way that allows you to play your high end AAA PC games processed on the PC but video streamed to the shield and controller intput fed back to the PC, so you can play in another room on a big tv say, with pretty much no lag.
how you get an NWJS steam game working through steam link streaming to the shield I have no idea.
But would be happy to help you test if you like.
i found an old steam thread here with the same issue but it goes nowhere