Your correct seam allowance is the one that gets you the right size unit or block. I agree that you should check that by sewing pieces of fabric together and measuring the result, as in the video below. People get stuck on the idea of the 1/4", but if your seam allowance is a perfect 1/4" and your blocks are coming out the wrong size, that's not an accurate seam allowance.
https://www.youtube.com/watch?v=H_A1uPdqfsI
It takes time and practice to become accurate and consistent in your sewing, so don't be discouraged.