Can high-tin bronze be made sharper than low-tin bronze?
Unfortunately I don't have a solid reference for this, but what I remember from my undergrad courses is that the limit to sharpening is basically determined by the porosity and tensile strength of the metal you are trying to sharpen. At some point you will just run into the microscopic roughness of the metal itself and that is where sharpening ends.

Low- and high-tin bronze are pretty rough classifications so I couldn't tell you which will result in a lower porosity or higher strength, but if I would have to guess than I think low-tin bronze can be made sharper, because copper has a higher strength than tin.

Maybe if you can get your hands on this book chapter, you can find out a more exact answer.