One thing I believe all should be aware of is all sums are not created equal. A sum like 14 has something like 50 straight numbers associated with it as opposed to sum 0 or 27 which only have 1 number. So sums 10 through 19, etc. are going to appear more frequently than sums 0 or 27, but also have more numbers associated with them. Its kind of like the game Battleship, trying to hit an aircraft carrier is easier than hitting a small patrol boat. I would upload a photo of the sum straight bell curve but I can't here. You could Google "Pick 3 sums bell curve" and you might be able to find one. Also you could just go to the Lottodds Prediction page I believe and filter each sum from 0 to 27 and copy all the numbers you come up with and you would be creating your own sum bell curve.
I'm trying to play straight, eliminating numbers like sequential, etc. Also groups of straight numbers exist within each sum. Might look for sum patterns and then play maybe 1 to 3 sums that seem to be related, trying to find the right balance, etc.