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There would be frame lag because normally you'd draw to the surface in the step event and draw the surface during the draw event, both occurring in the time slice. By splitting the drawing between consecutive draw events, the same operation takes twice as many time slices. Whether your logic is updated each slice, or alternate slices, there will be one or two frames of additional input lag as well.
There is no guarantee that the image will be preserved for the next redraw. I don't know, but my suspicion is it probably won't work on mobile devices. If it doesn't, you'll need to buffer it yourself which would mean at least one extra screen-sized surface.
Abusing forum power since 1986.
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Well doubling the event pace also doubles all calculation gamemaker does behind the schemes. - Better would be if you could just havea "pre-draw event" that your engine is certain to be executed BEFORE the rest of the game (obviously different pre-draw events don't have a given order, but then it would be obvious to have those events not depend on order anyways).
In the very first draw event one can simply draw to the surface .
Also each surface should be capable of redrawing itself at each draw event: otherwise you have a 50/50 chance your game goes boom if a screensaver pops up or another game gets focus.
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