Id go with lemon tetras over diamond tetras, the splash of red over their eye is really pretty with all the green of the plants and from what Ive searched around lemon tetras are supposed to be pretty peaceful.
And yeah.. discus while gorgeous are a handful to keep, I think you're doing the right thing in gearing your tank towards them but waiting before actually getting them. A beautiful and healthy planted tank with dwarf cichilids, tetras and cories is plenty to look at already and can be a total gem without any fish beyond that.
Yeah and I think I;ve read Lemons are better schoolers and less nippy or other fish. And they stay smaller, which I like.
While talking to my LFS they tried to convince me that the Kribs and Rams would outright eat the Rosboras? Is that correct at all?
Certainly, I still hope to get discus, but I feel like placing them, in a newbie planted tank, is a rather tight line. Especially with their low tolerance of nitrate and such, which is usually higher in planted tanks. So I'll just see how it goes!