I have never had any problems with the Betta jumping out-even in the grow out tanks with 50 or so juvies that go in attack mode anytime you go near the tank-jumping out of the water at you and in my case....the cats that drink out of one of the tanks on the lower level that I only have one light strip on. I think my cats feed them by dropping cat food crumbies in the tank and why the Betta respond to them the same way they respond to me....lol.....Anyway.....when you use 2 light strips it covers the bigger part of the top of the tank...Plus when you have floating plants this helps the Betta feel more secure so they are less apt to jump out.
As far as evaporation.....I have to top off all my tanks weekly due to evaporation using the open tops.
I have never had any condensation issues on anything or caused any problems with my light strips and some of my light strips are well over 10 years old and going strong. You can buy special attachment to prevent any moisture issue on the end caps-but I have never used them...I have had the light strips fall in the water and still working without issues...lol...cats.....gotta love-em.....
I like using the open top method for plants due to better light penetration-
On one that I have to use a hood on-I removed the lid part and the plastic partition where the light sits for the two light strips I have over that 10gal.
You don't have to use 2 light strip-One is plenty 20w on 10gal will give you 2wpg.
On some I may have 2 but only turn 1 on or alternate turning them on. With 2 20w on a 10gal that will give you 4wpg and that is a lot of watts on a tank without injecting CO2-usually this will cause algae problems-but with mature soil based NPT the decomp from plants and other organic create natural CO2 that can help prevent algae.
With planted tanks-its all about balance especially in the soil based tanks