New version of Shapespark includes indicators in the Objects tab to help to assess the size of the scene:
You can hover the mouse pointer over the ranges borders to see the numerical values.
The scene with all the indicators in green should load well on lower-end devices.
These indicators are a hint, not an exact science, memory available on devices depends on the hardware and the number of other applications that run together with a scene. but hopefully the indicators will help to quickly check if a scene size is within a reasonable range.