I am still reading so you may have already had this info, but the only way to get GMO free feed with our current labeling standards is to buy organic. Organic standards prohibit GMO grains or other foods. Most non GMO feed providers will tell you that they are either corn and soy free (the 2 biggest GMO grains). I get GMO free and not organic feed most of the time. The cost of GMO free feed can be a challenge at times, but it is worth it.
I think Organic is the best bet to get the least chemicals, but have been told multiple times that there really is no such thing as GMO-free corn or soy anymore ... It all gets mixed up by nature, etc. It really peeves me there isn't a "choice" any more.
Also, if buying soy-free vegetarian feed it might be Canola protein ... Canola is just as GMO as soy.
Field peas don't start at a very high protein percentage, so after mixing in the nutrients needed for digesting them and the other things the chickens need, one doesn't end up with a very high protein level.
There is a lot to consider.