Assume you have OEM or equivalent springs. I doubt they were upgraded ever. In this case you want the KYB GR2 struts. There is no reason to spend the money on the KYB AGX struts if you're going to use those springs for the foreseeable future.
You seem confused about the KYB AGX struts. They are adjustable, and the fronts have 4 different settings. The first setting is the same as the KYB GR2s, settings 2, 3 and 4 make the strut stiffer as you raise the setting. There is no way to buy "AGX level 1" struts. They are adjustable.