I have not had the pop up disturb me since I turned off notification. You should have seen it like I could not complete any task I was doing...even while I was watching a show...that was the last draw.
Why would you not want to enable RCS? RCS is infinitely better than SMS. Just look up RCS and the excitement around it on various tech sites and forums like Android Police, Droid Forums, Android Authority, 9to5Google.