Godzilla’s size has varied wildly across his entire history. As long as he acts like Godzilla is supposed to act I’m sure Universal can pick whatever size they feel would work. As for physical representation we would never need to see him all at once. One physical scene we’re up in a building and see him glare at us through a window, maybe another where we’re at street level and just see his feet and maybe a bus falls down that he just destroyed (BOC reference), etc.