The table grows in size depending on the number of columns. Internally the table is just a bunch of arrays, and there are no additional composite objects so I would't expect the serialized state to be significantly larger than in 2.x.

With that said, doing one network call is generally better than doing many. I don't know how we would handle the case where there are cache misses, as writing the single large structure multiple times could get expensive. Of course all of this can be made moot by having console tasks that allow you to warm the schema caches.