Sometimes when I drove on the highway, I felt my max drifting left and right.
I don't know it was caused by the wind or not. But it shouldn't be the tire balance problem (the tires were rotate and balanced recently)

Do I need to do the alignment?
Or anything will help to improve the stability? (FSTB?)

 

If its alignment, its not going to drift both ways, its going to drift towards one side only.

You were probably in heavy winds. FSTB will help keep the max tight in corners, now much difference in wind.

Dixit