Pressing seams to one side gives strength to the top. However, there's nothing wrong with pressing open if it eliminates bulk. Just remember you won't be able to quilt in the ditch if you press them open. I might suggest shorter stitch length in piecing and dense quilting if you press all the seams open.
I see that you say you are in Eastern Oklahoma pining for Massachusetts. I grew up in Eastern Oklahoma and spent 36 years in Western Oklahoma. Am now in Northern Virginia and miss the slower pace of Oklahoma.
Jane