Since you have a Le6921, I will say Geissele SSA ( or the lower cost version 2-stage) is the way to go if you want to spend money.
They are not adjustable, but they will pass drop test without discharging. Hence they are ( the full auto version) purchased by cops and military.
I run both version as a precision trigger or a general trigger, and I am not sure it is any more meaningful to get a split time lower 0.12 for a general rifle, unless you are looking for a dedicated comp gun and need a straight trigger bow.