Well, ARMS doesn't look all that graphically intensive, even in comparison with Pokken. But I think another aspect that will makes it perform better is the local multiplayer aspect- Pokken's way of managing non-split screen play was convoluted, but the portability of the Switch circumvents this.
Some interesting notes:
-The unique elements of characters seem to revolve around their movement options, with the only exception being Master Mummy's shielding gimmick, which allows him to regenerate health.
-Dashes and Jumps charge punches for a brief period. When charged, ARMS gain faster punch speed and secondary effects- the Toaster, Spring Man's default, causes knockdown and a burn effect. The Shocker, Ribbon Girl's default, causes both arms to become stunned, leaving characters open for a follow-up. Mummy Master's default both cancels opposing punches and continues to travel.
-During the Treehouse demo, it was confirmed that there will be additional weapon choices for characters outside the three stock choices featured. It's unsure if all characters will be able to use all ARMS, or if certain ARMS are relegated to certain weight classes. Master Mummy and Mechanica seem to be able to utilize heavy/large ARMS, for example, but Mechanica can also use Toasters.