Speaking as a newer trap shooter, but a very poor one for as long as I have been at it, full 1 -1/8 12 gauge loads make a difference. You can shoot reduced loads, but expect reduced scores, which makes little difference if you are only competing against yourself. I took a lesson recently with a guy named Phil Ross and since all I had was 1 ounce wads that was what I brought. He suggested I go to "soft 1-1/8's".
If you have these #$%^& bio targets, I think full 12's are even more important. Whereas a 1200 fps 1 ounce load breaks them, a 1250 fps 1-1/8 crushes them.