Holes are a trial and error thing. Start off with like 20 holes, and stabilize the habitat by leaving it alone for a little and checking the temps/humidity. Add more holes until you get it right...if you add too many holes, nothing some tape can't cover up. As for a lamp...When I used individual tubs I just used an UTH and that was enough.
Here's what my set up USED to look like...
The ceramic lamp is not turned on, it was just there because I thought I needed it.