These are interesting videos from April coffee (using Kruve Sieves) and lance Hendrick (his competition brewing method reducing the impact of fines). Personally I didn't find any benefit in sieving with a steel burr Vario, commandente and EK43. I guess the benefit maybe different depending on your grinder and what you are looking for

I have done quite extensive testing on hand grinders to answer this question.

I used Kruve sifter for my tests. Just to note, I am an experienced home barista and not a Q grader...

When all fines are removed, total surface area of the coffee particles significantly reduce, thus you need to change the brewing parameters to compensate this...i.e. increase amount of coffee, grind finer, increase water temperature, longer brew times, more agitation,etc...

If you keep all brewing parameters same and just remove the fines... final cup will be dull and missing complexity...

I cannot say how much fines you need but based on my experience, most of the top notch hand grinders (Comandante, Kinu, Timemore Chestnut X, 1Zpresso K, etzinger etz-l, etc...) produce less than 10% fines... and this helps to get a more balanced cup...