I can see the station 2 can pin the screen in space with 3dof, but only for the apps playing on it. Will I be able to connect any device to the station 2 and be able to fix its screen in space?

No, because Station 2 doesn't support DP-in. The screen anchor function can only be realized when Rokid Max 2 is connected to Station 2.If other devices support screen projection, you can project the screen to Station2 and then fix it in the air.