Recipes call for cups of flour. Other articles I have read talk about weighing your flour. How much weight does one strive for per cup and does sifting your flour enter into this equation?
When you use cups things can vary depending on when your recipe was printed. Earlier recipes (often pre 2005) use the "scoop and sweep" method, where the cup measurement is dipped into the flour container and a straight edge/knife is used to level the flour with the top of the cup. Currently, most recipes use the "spoon and sweep" method where you spoon the flour into the cup and then use a straight edge to level the flour with the top of the cup. You would sift the flour into a container first and then measure out your flour no matter what method you use.
The weight difference between methods can be an ounce or more depending on the flour. That's why most people will tell you to start using a scale for peak accuracy.
Here's a link to King Arthur's measurements that may help with cup measurements and weights.
Most people take a cup of flour to be 120-125 g. For consistent results, sift directly into the measuring cup, then level off with a straight edge.
a lighter fluffy cup of flour. It actually weighs less than an unsifted cup of flour.
Flour can settle and compact with time. Cup sizes can also vary from country to country.
A sifted 125g of flour will weigh the same as an unsifted 125g of flour.
With weighing flour, I know I sift less often (sifter is in some deep dark kitchen corner) unless I want to remove any foreign particles or large bran bits.
I spent more than a year eyeballing pinches and tsps and tbsps and cups. Then I almost murdered my sourdough starter. I never wanted to be a guy with a scale, but, to figure out what was wrong, I needed one -- and the scale changed everything. Honestly: get a scale. It's that transformative.