The Amazon Fire TV Stick 4K Max supports an output of up to 4K resolution at 60 frames per second. It is, however, the wide HDR format support – Dolby Vision, HDR 10, HDR10+, HLG – that makes it one of the best buys. As for the audio, there is support for AAC-LC, AC3, eAC3 (Dolby Digital Plus), FLAC, MP3, PCM/Wave, Vorbis, and Dolby Atmos. Unfortunately, the stick supports ARC and not eARC. Therefore, the Dolby Atmos experience is limited to compressed and not lossless format.
Important to note that the Fire TV Stick 4K Max’s UHD resolution and HDR capabilities are screen-dependent. Therefore, the stick automatically adjusts the resolution and HDR based on the connected screen capability.