Using nr 1 and 4 of the last couple of sketches I tried to make some kind of hybrid of the two, using mostly nr 4. I also received some feedback saying buttons should have drop shadow, to make it clear they are buttons, so I added that to see what it looked like as I was skeptical.
I must say I prefer the original nr 4 (top left without drop shadow). The one below it, with the lines, works, but I don’t think it follows the style quite as well. I am also very unsure about the drop shadow in general, it does make the buttons pop a bit more, but I don’t think it works with the style. In conclusion, the old nr 4 is the style I will be going for, but I will experiment some with shadows and other ways of making buttons pop out as I go.