Greetings.
I built one of the Acedemy/Minicraft 350th Titanics for my dad about 10 years ago. I also put lights in it, and during that process, I played with a lot of different setups.
I finally settled on just 3 low voltage lights, in the hull only. Part of this was because wiring more of them into the upper decks was getting tedious (I tried), but ultimately, I abandoned them above the hull because of the way that the light bled through the plastic. I even went so far as to paint some of the interior (inside) walls black/other colors, and although it worked to block the light, masking off all the windows had added up to a really, REALLY big hassle. It wasn't worth it for me, so I settled for what I had.
Although I could have done more, I thought it looked good enough.
I'm also one of those that has a hard time completing kits because I'm always adding and adding and adding... And I get pretty indecisive sometimes when all the possibilities start spinning around in my head. Sometimes the best medicine for me is to just toss it together and not try to make the perfect model... One of the disadvantages of ADD, I suppose.
Best of luck.