Don’t complicate things. If you’re planning to downgrade both the Hellcat and Achilles tank destroyers to Tier 3, then I don’t think there’s much to discuss. Germany distinguishes between medium tanks and tank destroyers as offensive and defensive, while American and British tanks and tank destroyers both have turrets, roughly equivalent firepower, and tank destroyers often have larger caliber guns. Aside from differences in armor protection, these American and British tank destroyers are essentially no different from tanks.