Good Morning. On this subject, I can only speak for myself. I did all of my ( K1 & K2) visa applications myself. I also did my AOS myself. I had one RFE on the I129 form( I knew it was going to happen )
I think you will be fine if you research and learn to listen to a few of these good people here on this website. I save myself well over $5,000 in savings just doing it myself