Seeking advice, seamless terrain edges

The goal is to have multiple terrains (just planes that have been subdivided) and have their border vertices line up with each other throughout sculpting.

Things I have already tried:
• I saw other posts where a shrinkwrap using a vertex group was used, but this seems like more of a fix for when the vertices are already close. If I move a vertex too far away, the snapping fails. This of course is because it calculates the distance based on the original position of the vertices instead of updating their position based off the effects of the shrinkwrap itself. Not a fault of shrinkwrap - just how it works.
• I tried looking around the geometry nodes for something, but came up short.
• sculpting both objects at once. This would be the best fix if it worked, but it doesn’t look like you can sculpt multiple objects at once. You can only switch between them.
• Sculpting as much as I can on each terrain, then going back, selecting the border edges, and scaling them to 0, then soft select moving them into place manually.
• avoiding the edges as best I can in sculpt mode, then going into edit mode for both objects selected together and moving the vertices into place by hand (since I can select vertices from both edges at once). This method is tedious.
• doing it in Unity using their terrain tools addon. The only problem with this is that it does not triangulate the terrain the same way I do, which results in jagged edges when you do cliff-like areas where there is a hard edge. I tried looking up how to possibly access the actual mesh data of the terrain data objects because it’s not beyond me to write a script to rotate the triangulation edges, but I came up short.

and lastly, the best method I have come up with:
• joining objects, merging vertices, sculpting, splitting by edge, p to separate. Basically temporarily making it one object to sculpt, then separating it again. The trouble is keeping up with exactly where to split it since the terrains have so many subdivisions. Definitely works though.

I am looking for any tips or tricks to make this easier upon myself because I have an absolute ton of terrain modeling that needs to be done over the coming months. I would strongly prefer to stick to Blender and am not all that interested in trying out any other outside tools, mainly because I’ve spent so much time already trying different things out and I really need to buckle in and get this done.

Thanks in advance.

You can try masking the borders before starting to sculpt, so they stay all the same.