We know there are quite a lot of sizes. But the fact is, every one of them has some purpose.
The size of the hardware device (.NET or USB) determines the hardware drawing size. This is the maximal drawing output size you can achieve.
Every virtual device has its own size, because you can have e.g. 2 virtual devices drawing on one laser output. And you can define where each of the device is drawing.
And finally there is a real time size you can use in live mode. I know, it doesn’t actually look good when it’s used while performing live show. But I remember having some shows, where the client wanted to draw “something, somewhere, immediately”. And that’s what it’s good for.