Perspective view / screen size

When you create a new View in perspective it automatically sizes it to 800 x 800.

I’ve changed the sizes to mess around with the module but does it really matter what size you use? I have been using the main view as column then adding other containers inside that.

Depending on the container type, that size is used, yes - mostly by coordinate containers (in fixed mode), but also by all container types when you drop a view into another view as an embedded view, or when using things like flex repeaters (hence the option to useDefaultViewWidth/Height).