Screen is defenetly a bad idea any humidity you build up will evaporate quickly.
Your best bet would be to use glass or plexy to cover 95% of the top, and use a screen area for ventalation. I have seen a lot of dart tanks with that set up and it works really well.
As for droplets either except them as giant rain or it is possible (but harder to build)to place the top on an incline this way condensation builds up and runs away possible to a collection point or just to the pool end. Like I said it will be hard to build but is an effective way to provent droplets.
Good Luck
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Jeremy
"I am become death, the destroyer of worlds" July 16, 1945 Robert Oppenheimer
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