If the objective is very similar, good engineers will independently arrive at a very similar solution.
Yes, the Northrop engineers knew of the Go-229 / Ho-IX. But Jack Northrop has also played with flying wings before – witness the YB-35 and YB-49. Unfortunately, those designs "did not fly" with the conservative bureaucracy of the Air Force. While the Ho-IX was a very advanced concept, there was no "secret" in its design, so how a low RCS airplane should look like was quite obvious to the Northrop engineers.
That the B-2 looks more "edgy" is caused by more insights into stealth technology. While the Horten IX tried to minimize frontal area, used wings of wooden construction (which are transparent to radar energy) and Reimar Horten had planned to use radar absorbing charcoal, the B-2 uses edge alignment in order to reflect radar energy at specific angles, besides using radar absorbent material. When Northrop was designing the plane, it had a rhombic inner section with rectangular wings, much like what is now shown of the new B-21 design, but the small chord at the wing root created a structural weakness when the Air Force added a low level flying requirement. That only was overcome after Boeing got involved. Boeing engineers changed the planform to the current shape by adding more chord at the inner wing which resulted in the typical "W"-shaped trailing edge of the B-2.
B-2 design evolution and its Lokheed competitor (picture source)
After the B-2 production run had ended and after Grumman had merged with Northrop, a full-scale RCS model of the Horten jet was fabricated by Grumman engineers with modern techniques to simulate the aircraft as it would appear to electromagnetic energy. It was tested at a RCS test facility, using similar frequencies as those used in WW II. While the design did show a markedly lower RCS than comparable airplanes of the time, this can be fully attributed to its shape and the use of wood.
Horten IX replica on a sting at the RCS test range (picture source)
Reimar Horten was a bit dogmatic about his designs and insisted that they only use a wing and not even a vertical tail, even though this would had benefited its flight stability. As it turns out, a straight vertical tail produces in combination with a wing or the horizontal tail a nearly perfect corner reflector. While this dogmatism helped to reduce the airplane's RCS, it resulted in marginal lateral stability.