why does my cream puff with sable dough doesn't come out nicely and also doesn't have a beautiful crack on top?

When I'm not going to bake pate a choux right away, I definitely chill it. Usually, a slight rest doesn't make much of a difference. When mine don't turn out, it's usually because the oven was either too low putting them in, I didn't leave them in long enough to dry, or the consistency of the batter was off a little (it's a guessing game until you nail it a few dozen times). Also, you hit on something when you mentioned piping. While that shouldn't make TOO much of a difference, I always tell people to pipe the shape you want the final product to be. A flat disk takes more work to rise than does a round mound, so if you hold the bag ½" or so off the sheet pan and just hold steady until you have a nice "mound", that should work better for you.

When I look at your photo, they don't look bad at all....but I would venture a guess and say the oven isn't hot enough. If there are multiple people in and out of the ovens, or you put your pan in after it has been open for a period of time, the burst of heat that choux need is going to escape before you can utilize it. I always put mine in at 375 - 400F (depending on what I'm making), and leave the oven closed for a good period of time (often 10 - 12 minutes). Keep us posted!