Both shows seems to be homages to classic tokusatsu films/series. Both feature a huge kaiju(s) that needs to be defeated by the protagonist and co.
Gridman has significantly less action and seems to rely on giving a surreal or mystery feel to the show. The CG designs are notably much cleaner, but very wonky in terms of movement.
The Godzilla Netflix films are more action-oriented and set up a post apocalypse sci fi setting. The films are all "CG-fied" but have significantly better flow in terms of movement.