Great discussion here on bench dimensions. I agree with Benoit on how the bench depth isn’t as important as we think. My bench is still not done after several years. BUT I am still using it as a work surface. Lately the front apron has been my benchtop with a little $20 HF vise clamped to it. Surprisingly, I only actively use the square foot nearest the vise most of the time. The whole long remainder of the surface is just to put down tools or wood on.
So to the OP, if you haven’t decided on bench dimensions, go with the generic bench dimensions recommended by Mr Sellers. As you work building it, you will figure out what is a good working height for you. And believe me, you will learn so much about yourself! I am making mine a little taller because I like working higher.