Sometimes you need to talk to a person instead of watching u-tubes. I don't pre-wash my fabrics but I do starch and press my fabrics before cutting. I have made many Bargello quilts and never had wonky strips. A quilting friend showed me something that she does with placemat of the ruler but it is too difficult to explain in words. That change made my piecing much more accurate. I also prefer to oversize my blocks. Takes more time but then it is accurate. I find most of my problems with quilting occur from ironing. Hope you are able to find what works best for you.