I just saw your new upload and watched and skipped 😛 and saw you stuck because of tons of gameobject & i just got a raw answer about how actually the minecraft game works ( Not sure , just theory , but can really work like charm with increasing to max framerate) .
Boom : I think minecraft creates only one object of 16 / 16 chunks . Else is all algorithm .
Hehhe all out of head , heres the explanation taking reference to unity .
We can create a mesh in unity by scripting . What mesh is actually vertices / triangles / uvs .
Now instead of creating / instantiating a new block of different/same types and combining them to create chunks , we can create a 16/16 size of big block/cube by some algorithum that will be a mesh cube which will have 3d grid ( nodes / subnodes ) (. These nodes will be assigned as a reference to cubes) . But in reality the whole thing will be as one mesh / gameobject . And then again by a some algorithm we can set the texture to uvs according the visible surface . i.e. the visible subnodes of a node(cube).
Now while playing , if want player wants to dig we can just simply update the position of the 4 visible subnodes of node(cube) and set new uv according to new visible subnodes of node.
Kinda confusing but , if you think as center as node / cube having subnodes on corners