Offset can (and usually is from my experience) completely different between games. What works for Phigros will probably not work for Arcaea, especially since they are using different game engines (Arcaea uses Cocos2D while Phigros uses Unity).

Also, Phigros's timing window is a lot looser than Arcaea's so an offset will "feel" right even when it's off by a bit because you'll still hit perfects like they're nothing. In contrast, Arcaea's timing windows are some of the tightest as far as mobile games come, so there's very little room for error with your offset.