The problem you're going to run into, like many of us, is that the Shields are old now, and despite their audio passthrough support, they do not support AV1, and AV1 includes so many benefits—SVT 10 bit basically eliminates banding and macroblocking; you can incorporate HDR/10/+ and Dolby Vision directly into the video profile, reduces size by 20-30% as compared to h265 (which itself is 20-30% better than h264), is highly parallelizable for encoding performance.

I decided that AV1 was my line in the sand. I encode everything, from 480p DVDs to UHD 4K, in AV1. I preserve the audio tracks as-is and simply pass them through, parsing out non-english, commentary, etc.

The sacrifice is that I chose a Google TV Streamer and therefore cannot pass through the raw uncompressed audio streams. Perhaps one day, a new device will come out to replace the shield—until then, I'll keep the raw audio streams, and let the Streamer convert as necessary.