I’ve never seen naptha (i.e. Zippo lighter fluid) do anything to any painted or finished surface, nor any of the plastics I’ve ever tired it on. I’ve been using the stuff in that context for decades, to the extent that I literally purchase it by the gallon. (I also use it in my lighters, because painter’s naptha is like 2% of the cost per volume of brand name Zippo fluid despite being the same stuff.)

WD-40 contains nonvolatile oils that will leave a difficult to clean off residue behind and if you use it on anything porous it will soak in and possibly stain the surface while being functionally impossible to remove without using yet more solvents. For that reason it’s not really a great way to get stickers off of things, especially things that you’d like to remain non-greasy or may need to stick something to again at some point in the future (paint, tape, etc.).

Naptha will evaporate entirely on its own given enough time, and you can even use it on paper and printed surfaces (excluding inkjet printed things, in my experience, which it will smear) with no harm done after it fully dries.