Question Filtering Probuilder mesh vertices

Hello there,
I've stopped upon small problem when it hits me with big performance and Can't seem to find good solution.

Given this image: I have two Probuilder meshes (red and white)


Legend:
Red - path mesh
White - terrain mesh
Green points - vertices of the terrain mesh
Yellow line - shows how many vertices are at the same position (4)
Brown line - shows omitted vertices

I'm trying to find out the best way to filter out terrain probuilder mesh vertices that don't share the vertices with the path probuilder mesh. Secondly, I want to somehow collapse shared vertices on the terrain mesh as there are 4 for each vertex position which is unnecessary calculations later on but can't find out a way to do it.

I'm using Probuilder API via script to achieve this goal.

This is the code that generated meshes on the image.

Code (CSharp):

1. void Start() {
2.     quads.Add(ShapeGenerator.GeneratePlane(PivotLocation.FirstVertex, 1, 1, 1, 1, Axis.Up));
3.     quads.Add(ShapeGenerator.GeneratePlane(PivotLocation.FirstVertex, 1, 1, 1, 1, Axis.Up));
4.     quads.Add(ShapeGenerator.GeneratePlane(PivotLocation.FirstVertex, 1, 1, 1, 1, Axis.Up));
5.    
6.     quads[0].transform.position = new Vector3(0, 0, 2);
7.     quads[1].transform.position = new Vector3(1, 0, 2);
8.     quads[2].transform.position = new Vector3(2, 0, 2);
9.  
10.     ProBuilderMesh path = ShapeGenerator.GeneratePlane(PivotLocation.FirstVertex, 1, 1, widthCuts, heightCuts, Axis.Up);
11.  
12.     path.transform.position = new Vector3(2, 0, 3);
13.    
14.     ProBuilderMesh terrain = CombineMeshes.Combine(quads, quads.First()).First();
15.  
16.     List<Vector3> terrainVertices =terrain.VerticesInWorldSpace()
17.      .Where(vector3 => !path.VerticesInWorldSpace().ToList().Contains(vector3))
18.      .ToList()
19.      .Select(
20.         vector3 => {
21.           Instantiate(gameObject, new Vector3(vector3.x, 0, vector3.z), Quaternion.identity);
22.  
23.           return vector3;
24.         }
25.       ).ToList();
26.   }

Is there a better way to find out only vertices that are not shared with path mesh vertices and how to reduce amout of vertices for mesh??