It needs 64bit OS (e.g. proper kernel, userland, drivers aka modules, etc).
You've a better performance due to using the wider bus and more addresses. However, you need 64bit packages for that (which should be no issue for arch packages) and the effect is not that much more as already reached with the better SoC.
You can compare it with Windows and the effect of better CPU and/or 64bit OS vs 32bit. RAM addressing is no issue here but is only one effect of many having 64bit.