I've encoded roughly 270 movies with about 400 more to go. If metadata is stored on internal storage and cannot currently use adapted storage, at what point or quantity do I encounter memory issues on the 16G version of the Shield?
depends... metadata at its core is mainly text which you can pretty much ignore (should only add up to Megabytes at best). Posters (covers, backgrounds/backdrops, banners) will be different, there it depends on the media quality.
Plex usually downloads posters from The Movie Database -- those are usually 1000x1500px for posters and 1920x1080px for backgrounds. Sizes can vary but tend to be in the range from 200-500 kB (avg. 350 kB). So your 16 GB storage might actually become a bottleneck when you approach ~40,000 items.
However... Plex will also keep some copies of posters it found during matching. I've just checked out some of those packages. In my example, that's another 350kB (for a whole bundle of poster/background icons at lower resolution). This brings you down to sufficient space for "only" ~20,000 items ;)
The actual true bottleneck/drain is if you activate local media assets. Plex will manage copies of those in its library (so you have them in your filespace along the movies/media files and they'll be stored in the library). If you e.g. download high-quality album posters from iTunes or use background images from a Blu-Ray Disk, those will be much bigger. Real world example w/ 2 posters (4-8 MB each) and 1 background image (2.5 MB)... adding up to ~17 MB. Lets assume you're more organized than I am and stick with 1 local poster and therefore assume it's only 8-10 MB. So if you use all your 16 GB of internal storage for Plex metadata alone w/ local media assets activated and widely used, you'll get to ~1,600 items.
I appreciate you answering this. My library consists of mostly DVDs, 95%, and the balance in BD. Not a huge library in comparison. I'm not expecting to download too many apps on the Shield. So based on your theory, I should be fine with the 16GB version.
With your setup, I believe you'll be ok with plenty of space remaining.
I have 2200 movies in my library. I reset my PMS not to long ago & after all the metadata & so on was added, My PMS was around 3GB-4GB in size. Once I added 45 full tv series, Its went up to 6.2GB.
I have my Shield Tv rooted & PMS reinstalled to 250GB SSD adoptive storage, So I have no need to worry about space. But I believe if you have PMS on internal storage, You need to keep at least 2GB-2.6GB of storage free, Otherwise you'll have trouble installing Shield Tv system updates, Random errors & system wide slow downs which will lead to the Shield Tv crashing every now & then.
Again, thanks for your assurance. I disgust this with others outside the forum and they said the same.