I like precuts and buy them before yardage. Easier to store and I have one print or more of the whole line. And they look so inspirational on my shelf. I want to get one and start sewing. I use steam and press them. I put a piece of muslin on the ironing surface so if any bleeding happens I will see it.
Fabric will shrink in one direction. If a jelly roll it will shrink in length not width. So depending on how the pre cut is cut depends on grain line when cut.
I don't use layer cakes or charm squares if I need exactly the square size.