Do you really need to iron 1/4” seams before nesting?
 

I saw on YouTube that Jenny Doan doesn’t iron after sewing 1/4” seams and then joining them to another 1/4” seam. She just holds down the seams and nests them this way. If I do that, will I get a true scant 1/4” seam or will it be off because it might not be laying totally flat? I always iron but if I don’t have to, I could work faster, but I want precision more than shortcuts.

I think you answered what is right for you. If you want precision, iron. I don't always iron and sometimes get a little lip of fabric that is easily quilted down. But the trade off is speed. Sometimes just piecing with the top seam away and the bottom seam towards is enough. Give it a try.

You can also try finger pressing the seams first (or use a wood iron). As with most things in quilting, try it and see how it works for you.

I usually press the seams but I have been doing them open my last several quilts. My "precision queen" is Sally Collins - she has some books, not sure about videos, but, I am still aspiring to get that precision.

Remember that Jenny is making a video. Some things might get skipped in the interest of time. For me, pressing as I go improves the final product.

i tried not pressing on my last quilt and it turned out just fine. i like saving that step. that being said, if it is going to be a show quilt, i will press constantly and trim at every step.

Try it both ways and do what works best for you.

What others prefer and do ..... does not mean that it is what you prefer and want to do!

I don't always press if it's just one seam, but right now I'm doing a 25 patch for an Irish Chain and those needed pressing.

For me, it completely depends on the type of block I am making. Often, when I am making LC blocks I will finger press or use one of those wooden cuticle pusher thingys between each round of logs. I will then press the block when it is done. But I tend to make 6.5" LC blocks and I also precut all my logs. I also only finger pressed when I made the blocks for this quilt: https://www.quiltingboard.com/pictur...t-t293883.html But all my HST units were pressed before assembling the blocks. Each block finished at 8" on this one. But for the most part I tend to press every seam before adding my next unit, especially when I am working with blocks that finish at larger sizes or where intersecting seams are a critical element to the design, like star blocks or anything with FG units.
As others have posted, you need to try a few yourself and see if you are happy with the results. Additionally if your goal is precision, pressing each seam will make a difference.