Well, I'm not certain on wave orientations towards development -- I'm not familiar with any research into it, if there has been any -- but I would think that the wave tilt has little to do with the potential for organization. Both waves are going to have similar wind fields, just with different orientations. Given that the prevailing winds are out of the east in the tropics and that the last part of a center to usually close off is the south side, I would think that the orientation of a wave isn't going to affect that much. However, if I had to make a call, I would think that the NW winds coming around the west side of a NW-SE oriented wave would probably lead to that orientation being slightly more favorable for quicker development. But, that's also an orientation you don't see that often, so how much credence you can put into that may be up for debate. Nevertheless, I believe there are more important factors, such as convective organization, mid-level banding & circulation features (thought to be important to the genesis process), and the amplitude of the wave, towards the genesis question.

As for the second part of the question, when two tropical waves collide going the same direction, it starts out as a constructive interference process on the west side of the easternmost wave and east side of the westernmost wave (in the N. Hemisphere) due to the counteracting wind fields. The waves could then merge and perhaps amplify at that point if enhanced convergence in the wind field is realized in the low-levels, but I don't think that the orientation of the wave plays a large role in this. Two waves of opposing tilts at the surface, NE-SW and NW-SE, are just going to have this same effect shifted in position or orientation; for between two troughs, as tropical waves are, you must have a corresponding ridge. Merger is possible, which can lead to enhanced potential for development, but there is a period of interaction first and I'm not sure that the orientation of a wave (or two waves) affects that to any large degree.

I will reiterate the caveat at the start of the post, though, and invite any of the other mets (calling HF, calling HF) to add their insight.
dude, i'm not a met. will be a climatologist at best... -HF