Is qss the only way to counter lux in team fights?

No. Dodging her snare and then jumping her works pretty well.

Are we talking about malzahar or ww? I do not recall a point and click suppression on lux.

No

You counter in champion select with a ban, it is the only thing she can not outplay.

You could buy boots; the faster you are, the less likely to be hit by skillshots

You could just get cleanse and leave that item spot for a banshees or..something else.

You can't move in a predictable fashion when facing Lux.