For the most part, you can expect ARMS to run at a stable 60 frames per second. However, Game Informer notes that after going hands-on with the title, it’ll drop to an unspecified number. While we don’t have an actual number, it’ll likely be 30 frames per second.
Update by DigitalFoundry
1080p/60fps fixed in Single Player
900p/60fps fixed in 2 Players Split-Screen
900p/30fps fixed in 4 Players Split-Screen
(=^・ω・^=) Kuroneko S2 - Ore no Imouto - Steam, MyAnimeList and Twitter - PSN: Gustavo_Valim - Switch FC: 6390-8693-0129 (=^・ω・^=)