I don’t think a procedural setup is worth your or anyone else’s time.
It always results in artifacts or bad meshes and sounds way cooler than it is.
That said. There’s a Mesh Slicing c++ tutorial that covers the basis of doing similar things.
Procedurally that is.
It’s a 1 hour live training that can maybe be adapted to custom runtime breakables.
If you aren’t at all an artist, then maybe that’s a better way to go for you.
But even being a 10% artist, 90% coder will result in you having a better end result by working the art…
Re the instancing.
You can make the breakables swap from instances to BPs via proximity like my plugin for foliage does.
That way you don’t always render the object with multiple bits or have to have non-instanced blueprints spread out in the level.
(Really though, there’s no adverse effect for having 100 or so BP thrown around a level, provided they have tick disabled).