I sew the HSTs oversize and trim. It may add some time and effort to the project but it is worth it to me in the end. I have tried the 7/8 and it never came out square or the right size.
Not sure what you are asking about the pattern. I often use the "It's OK if you sit on my quilt" book to pick out blocks. From there I decide on the size and the fabric. So I use a pattern but I also put my own spin on it. There have been occasions when I used a regular pattern but then I either made a booboo or ran out of the fabric and had to get creative.