- DO NOT leave it raw, as like you figured out, in time this will have adverse effects for sure. Might be good for even years but at some point it will warp or something. Bare minimum is treating it with beeswax, and properly!

- I have had bad experience with many acrylic lacquers, automotive etc. They dry fast but adding layers makes them surprisingly soft for a long time, so you need to have adequate rests between sprays. Have ended up with the lacquer wearing clear off within a year in spots; sort of rubbing into darkened areas and apparently never having dried well inside. Proper old-style brushed lacquer is much better, but it needs buffing for sure. Dries a week, but then you do get a real thick glossy surface at once.

I have just finished one neck with acrylic lacquer, and on this one I went for - instead of even trying gloss - matte. Did this by spraying very lightly, then using 000 steel wool to remove excess/level the surface, then repeated several times, until it seemed to me there was enough lacquer for certain to protect the wood well enough. So far it feels good and no problems.

And yes, just spray over the frets and clear them later on carefully, apply masking tape to neck surface so the frets only show and use steel wool.

Mind you, I'm no pro by any standard when it comes to finishing, I've just done similar jobs some half a dozen times. May not know what's the best way but at least I know some pitfalls to avoid :-)