Forget the Light Action. They're just a marketing solution to appeal to a recreational market. And you can pull out of Light Actions unintentionally, which defeats a big advantage of Spedplays.

Between the X series and the Zeros, to me it comes down tow hether you're comfortable with the wider range of free float in the X's. Some people do not like how the X's feel because of the huge amount of float. Other's adjust to this in a ride or two and its no issue.

If you don't like the wide amount of float, the zeros allow you to dial down the amount fo float.

As to x/1's versus X2's he difference is a Ti spindle versus stainless steel and about 48 grams. Personally I ride X/2's. My wife has X/1's but on because I picked them up used on Ebay cheaper tha new X/2s

I would not opt for the X/5's unless money is a real issue because the cro mo spindles in the X/5's can rust, and the bearings are not as good as the x/1's or x/2's