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.

Source

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

I just hope it isn't as bad as Sun/Moon's framerate issues. Dear god was that awful

How does a turn-based game have shit framerate? Wtf?

As long as it stays rock-hard 60 in single.

During doubles, the framerate would lower significantly. It was enough to make me stop playing doubles on 3ds

Lol..... I don't even think we should compare the Switch and 3DS hardware. 

And what does 4 player split screen multiplayer mean? Like 2 players use 1 switch, the  another 2 players use another switch for a 2 v 2 match? 

Thats pretty sad.

Good point. I always forget how weak the 3DS is compared to the Switch 

It is sad. It is the reason why I'm concerned for the 3DS still being alive. I don't want another Pokemon game to be pulled back because of technology from the 20th century

It's like a game of sources! Your link goes to a link which links another link for a source!

Oh I thought MK8D stays at 60fps?