I picked up the basic N95 equipped model to run as a little VM box and replace some Raspberry Pis, and yes it is most definitely enough to be a decent little plex server.

The alder lake iGPU can handle 4K transcoding to multiple clients at once, though I still recommend avoiding transcoding wherever possible. if your main playback device is the shield, you will very rarely, if ever, need to transcode.

I havent done any longer term testing as I use a larger purpose built system as my server, this little box is mostly running homeassistant and some linux VMs