You can run your bars at any angle that works for you. But if you angle them up too much, its makes the drops less usable, but it also depends on the shape of the bars. I keep my bars with the tops level, with the hoods level as well. I use SRAM hydraulic levers, which I love because there is a lot of surface area due to the large horns, so the crook of my hand is around the horn while the heel rests on the bar.
I always felt that perfectly level gave me the feeling of having to rotate my wrists down a little bit. So I always wanted them up just a smidge but not very much. Rotating them up quite a bit more makes the drops feel unsafe. But it makes the hoods feel better. But I have a feeling on a longer ride that would be too much pressure on the hands.