Help to create leavitating text effect

The text layers appear to be floating because they are at different distances from a moving camera and they also have some movement in Z so their distance from the camera is changing. When you combine the 2D background shot with a moving camera you get the floating effect.

The most efficient workflow depends on the shot. If it is a similar shot you might want to camera track the shot, set an origin and ground plane, then create a Solid and a Camera using the same points. You can then Shift + Parent your text layers to the reference solid, adjust their position so they are above the solid, then distribute them in X and Y. Just animate the text layer's z position slightly or add a slow wiggle expression like this to each text layer's position.

z = wiggle(.7, 40)[2];
[value[0], value[1], z]

 This will wiggle your Z position 40 pixels .7 times a second (slowly).

Create Camera Layer.

Create and distribute the Text Layers in the Comp, enabling the 3D Layar switch for each Text Layer.

Select all of the Text Layers and choose Layer > Transform > Auto-Orient... > Orient Towards Camera.

Keyframe the Camera Layer's rotation such that it does a subtle pan.

Adjust the position of the Text Layers as needed.  For the floating movement, try a Wiggle Expression.  Ryan Plummer over at School of Motion has a great blog on it: https://www.schoolofmotion.com/blog/wiggle-expression