FFXVI and XIV connection theory

[Iscah]

The Interdimensional Rift is just the area of non-space between space.
There isn't really multiple Rifts, nor is it a singular area. It's all encompassing in the same way "space" is.
The Void is used interchangeably with it, but I think refers more to the primordial energy aspect of it.
It is the capital N Nothingness like Chaos is in Greek Mythology.
Everything, including Space itself, was born from it, and everything will return to it.
In the beginning, there was only the Void, and the non-area it existed in, is the Rift, and the bubbles of existence it birthed are "not the Rift".

The void and rift not interchangable in FFXIV.

The void is the Thirteenth shard. The rift is the nowhere-space between shards.