Here’s the specifications: Device Specifications: Fire TV Cube | Amazon Fire TV
TrueHD not listed as a supported audio codec (same as all Fire devices). If you want passthrough for TrueHD & TrueHD + Atmos you’ll still want the Nvidia Shield Pro.
Ethernet port is 10/100 (same as all Fire devices). You’ll want to use 802.11ac/ax Wi-Fi if playing high bit-rate media such as 4K HDR Blu-ray rips, which can burst above 100 Mbps. Ethernet port on the Nvidia Shield Pro is 1 Gbps.
It supports AV1 video, as does the FireStick 4K Max. The Nvidia Shield Pro does not. If / when Plex adds support for AV1 video the hardware will be ready for it (see Plex Media Server 1.29.2.6273 - New Transcoder Preview).
I’ve friends & family members that use the FireStick 4K & 4K Max to access my server remotely. They are nice Plex clients. Unless a hands-on turns up a major problem, the Cube v3 should also work well with Plex.
