Not "offering" you KeyShot-- just correcting the perception you can't do soft lightbox lighting effects with it.

If I were you, I'd look at Marmoset and collect some standard HDRIs which already have the soft lighting you want. Also, because it's PBR shading, I suspect it would be simple to create a soft lightbox object(s) which you could easily drag around. Just create a plane and either give it a diffuse soft map or make it white and add a soft transparency map and set the material to emissive and voilà, you have your soft lightbox.