Mobilelawyer,
First, check out my post over HERE.
Basically Adaptive storage takes the drive, encrypts it and used that as your main storage basically turning your 16GB to 240GB SSD. That’s all it really does and really doesn’t anything do with your Plex (so to speak). The only think I don’t 100% is that even tho you select this, does plex still use the 16GB for some reason or do you just need to go into Plex (in the client) and set it to that.
In your case, I suggest just setting this up for Plex and just using it as removable storage and then go into Plex and set it to use that. If your are not going to do anything that is going to take up the base of the 16GB (doing shield stuff) then I would separate out your plex data. This will also give you access to your plex data for backup if need be.
This is my suggestion and other might want to chime in.
P.S. I have a testing shield and am going to set up adaptive storage and see what Plex shows me. Give me 10 Min.