Well i mentioned it many times already... here to make it easier for you:

3DGS version:
1) Open Med
2) Select the vertex you want to manipulate
3) Write the ID down so you remember
4) per script call your vec_for_vertex or whatever using the ID

Unity version:
1) Open your Model Editor
2) Select the vertex you want to manipulate
3) Write the ID down so you remember
4) Per script call your vertices function using "mesh.vertices[ID]"

Got it? Okay?
I'm not thinking in black and white (funny that i am saying this :O) but i just dislike it if conversations are like this:
Person 1: "Feature A is easier in Engine B than C"
Person 2: "No it's not you can just call this and that the same way"
Person 1: "Anyway it is SO MUCH easier in Engine B!"

Which isn't true. It might be i tiny slightly bit easier if you consider that you first need to store the vertices array in Unity before using it

Vector3 myVertices = mesh.vertices;

But that's it and as Slin said, it has other parts that makes it "SO MUCH" easier using Unity than 3DGS.

I never ever wanna start those engine a vs engine b conversations since they are just stupid, but if i feel that someone is spreading wrong information, i can't help and convince them they are wrong