'He has a soft touch' means he does things in a gentle and careful way. For basketball, this would refer to how he handles the ball. It can also be used figuratively, eg he chaired the business meeting with a soft touch.
I don't know basketball, but I think downtown probably refers to 'near or under the basket'.
This is from megayears of being a couch potato watchin' NBA games.
Someone having a soft touch : His shot when hitting the rim would often find its way into the hoop because the ball does not bounce hard off the rim; or the shot has a friendly spin that when touching the rim it gets into the hoop.
Shooting from downtown : Shooting from beyond the 3-point line.
If these phrases refer to basketball, I would suggest that 'a soft touch' is a good sense of accuracy in shooting, and that 'going downtown' is approaching the opponent's basket, probably quite closely, as in a slam dunk.
Apparently, no one has been able to define "from downtown." The reason they say this is because NOBODY lives downtown. However, when someone makes a lay up (scores from merely inches from the basketball), they might say, "He took all the way home." Thus, if he shoots from "downtown," it couldn't be anywhere near 'home.' So, yes, "downtown" represents the 3-point line.