Well, you’ll only hit a vein if you botch the injection. That happened to me with my first chip, because of an inexperienced piercer. The resulting haemorrhage was spectacular and worrying enough to prompt me to pay a visit to the ER.
Absent that, once the chip is in place, it won’t cause problems with veins in my opinion. I have a large chip in my right hand that ended up sitting directly on top of a vein, across it. The chip and the vein even made an X shape that was quite visible on the outside. One month later, the vein had rerouted itself around the chip. I kid you not, I didn’t even know that sort of thing could happen. The human body is remarkably adaptable!
Other than that, you need to leave at least 5 mm between your two chips. Also, as far as I’m aware, both the xNT and the xLED are uncoated: it means they might travel around under your skin until they reach a spot where they’ll settle
So if your xNT has settled near the thumb under the thenar muscle for instance, you might want to implant the xLED closer to the index metacarpal on the other side of the muscle, to promote possible movements on that side of the muscle only. If you implant the xLED right on top of the muscle and it goes on a hike, it might decide to “fall” xNT-side and end up sharing the same space.