No I do not think an elaborate plan makes a perfect proposal. Though perhaps that is just because my proposal was nothing elaborate, yet remains a wonderful and humorous story to tell our friends and children (likely the Grandkids will love it one day too). Long story short, mine was unexpected, I had just got done doing the dishes and teasing my then boyfriend about not giving him a kiss because he did not help. He replied 'I love you but you are going to feel stupid in a minute'. I had no clue what he was talking about so I said 'not a chance'. Then came the proposal, and I was standing at the time. So out of a little bit of shock and jitters I sat down, and immediately the kitchen chair broke. So there I was tears of joy, and a sore butt. Here we are 4 years later still going strong.
I think a simple proposal is perfect. An elaborate proposal is great, but I think the simple things are more memorable than having your ring baked into a cake, or delivered in a wine glass to a table at a fancy restaurant. There is something to be said about the spontaneity of a proposal that comes when it is unexpected and comes when the feeling moves the person doing the proposing!