The question then in context become if mask helps during those 2-3 days before symptoms appear. There is a few links above that links to the effectiveness against coughing and sneezing, but I would guess those are symptoms.

Nobody knows. We know that "real" masks (i.e. n95 or better) are effective when worn properly, but many people don't wear them properly.

The evidence for effectiveness of other kinds of masks in the prevention of virus transmission is weak, at best.

Unfortunately, respectable publications have been pushing that paper recently as proof we knew about asymptomatic transmission back in January for stupid, partisan, political reasons.

It's very easy to forget that current decisions and past decisions operate on vastly different kinds of knowledge.

It's easy to look back in time and say "Someone knew the right answer."

It's very hard to stand in the present and say "Of the 20 people who each have a different answer they believe is right, I am going to select the really right one."

Often, the optimal decision is to hedge and delay until information becomes clearer.

Anyone citing that paper recently is being irresponsible. It was debunked about a week after the pre-print went up on the server.