I know that my version has the new, fancy looking GTM Hippocrates model but does not have the new, fancy looking GTCv Deimos model, if that helps. And by fancy looking, I mean like totally re-textured. I also know that I definitely don't have FSO 19.0.0.
Get Knossos. It will let you be up to date with FSO and all its mods, also guarantees a simplified installation procedure. https://fsnebula.org/knossos/
Apologies, it seems I was totally wrong about everything I thought I was right about.
I
do have the latest mediavps and I also have Knossos. I also have FSO 19.0.0. Here's where things get tricky, when I launch Fred2_Open_19_0_0, it says in the application after it is open that it is actually Fred2_Open_3.8.1. When I launch Freespace2 from Fred2 it launches it as the version with mediavps 3.8, but then says in game that it is indeed running on FSO_19_0_0.
While typing this post, I had mediavps 4.0 in the Knossos launcher. Launching mediavps 4.0 had a problem where my custom missions would not appear in the single missions menu, as they do with mediavps 3.8. I just now updated to mediavps 4.1.23 because Knossos said they were available, and now when I try launch the mediavps 4.1.23, it say it cannot find an executable.
I would obviously like to play everything on the latest and greatest mediavps and FSO version, but I am afraid to break things.
Edit: I currently have both the Mediavps 3.8 and 4.0 folders installed in my FS2 directory. I believe I left both there because when I tried upgrading to Mediavps 4.0 without using Knossos my Fred2 wouldn't recognize it, and afterwards when I deleted the Mediavps 3.8 my Fred2 would launch FS2 as the vanilla version, which is also a problem because the vanilla version lacks a lot of backgrounds that the mediavps have.
Edit2: Crucial piece of info here, Knossos launcher says I have FSO 3.8.0-3, with no option to update, but in my FS2 folder I literally have FSO 19.0.0 installed.