pixels should have no more than 6-10 ft separation... the 5v data signal degrades over distance. some controllers are better and will cover more of that distance.
when a pixel receives the data signal, it not only generates LED light, but the chip regenerates that signal to get another 6-10 feet to the next pixel.
50ft is pushing it. but if you are successful getting to the first pixel, then all of the pixels after will have the benefit of a newly-generated data signal coming from that first pixel (to the second pixel)
i've not heard much about pixlite... just mentions this year. I've tried a SanDevice this year and liked it. For the larger distances it works well to send ethernet to the controller... and as long at the controller and the first pixel are within 6-10ft, you'd be ok.
i use Falcon products now, with pixelnet (to get long distances from hub to controller. the small smart string controllers are placed near the string where the distance to first pixel is rarely an issue.
one way to help with the distances -- "null pixels". basically, have one or more pixels between the controller and the first pixel you really want to light. these pixels don't need to produce light, they are used to regenerate the signal and get you a new 6-10ft to work with.